Siglec-7 Undergoes a Major Conformational Change When Complexed with the α(2,8)-Disialylganglioside GT1b

The siglecs are a group of mammalian sialic acid binding receptors expressed predominantly in the immune system. The CD33-related siglecs show complex recognition patterns for sialylated glycans. Siglec-7 shows a preference for α(2,8)-disialylated ligands and provides a structural template for studying the key interactions that drive this selectivity. We have co-crystallized Siglec-7 with a synthetic oligosaccharide corresponding to the α(2,8)-disialylated ganglioside GT1b. The crystal structure of the complex offers a first glimpse into how this important family of lectins binds the structurally diverse gangliosides. The structure reveals that the C-C′ loop, a region implicated in previous studies as driving siglec specificity, undergoes a dramatic conformational shift, allowing it to interact with the underlying neutral glycan core of the ganglioside. The structural in with studies show that binding of the ganglioside with key interactions and that the binding structure to of GT1b. The siglecs are a group of mammalian sialic acid binding receptors expressed predominantly in the immune system. The CD33-related siglecs show complex recognition patterns for sialylated glycans. Siglec-7 shows a preference for α(2,8)-disialylated ligands and provides a structural template for studying the key interactions that drive this selectivity. We have co-crystallized Siglec-7 with a synthetic oligosaccharide corresponding to the α(2,8)-disialylated ganglioside GT1b. The crystal structure of the complex offers a first glimpse into how this important family of lectins binds the structurally diverse gangliosides. The structure reveals that the C-C′ loop, a region implicated in previous studies as driving siglec specificity, undergoes a dramatic conformational shift, allowing it to interact with the underlying neutral glycan core of the ganglioside. The structural in with studies show that binding of the ganglioside with key interactions and that the binding structure to of GT1b. are a group of receptors that the of the family sialic a that the of of sialylated ligands siglecs to and in the immune and the of in the and expressed siglec to to of the and immune siglecs have in of to the CD33-related siglec and and the immune the of the to siglec sialic acid binding in the a that a with the sialic acid the binding the sialic the underlying glycan core key to siglec binding The binding preference for siglecs the and and glycan the in are for siglec binding are that of a to a sialylated a core the of neutral and sialic acid in of sialic acid expressed and to a and a of binding studies have that Siglec-7 shows a preference for acid and sialic acid The acid in as and have that a expressed to interactions with Siglec-7 expressed to the of the and in the and a have the structure of Siglec-7 as a template for the CD33-related siglec and the of binding for the sialic acid We the crystal structure of Siglec-7 in complex with a ganglioside structure reveals for the first how Siglec-7 with a complex oligosaccharide to a dramatic conformational in the of the the of the of ganglioside and the are in the are in the of Siglec-7 co-crystallized with a of the in the of the a of the glycan binding The binding and to the The C-C′ a the of the binding the of the glycan The of the that to the group that in a the the of are as are with the and are as the CD33-related siglecs and of of The CD33-related siglecs and in are in of the The as the of and the of are the with interact with the to in and of Siglec-7 of the Siglec-7 The expressed as a a The a and with The with to a of and the to of of for a in and to and with a of the with and in and and with a of to the and and the of the Siglec-7 structure with of and of of the in with in and and of the and the group of the into in the binding and The of and of with in the and of the for and of in a and of the a in a The into The for a in and the and and and the binding with of ganglioside in and to The in and with in with a of for and to the a the the with of to and and a with ganglioside in the of the oligosaccharide for the to Siglec-7 expressed as a The a structure that Siglec-7 co-crystallized with a in a group the The complex in a as to the with the and the complex The structure to with and structure of as that a and The glycan binding the in the binding for the allowing and the group to of the of the are in the the sialic acid of the of the binding reveals that the the of the binding the sialic the binding this and the a the C-C′ and the of the the of the binding and the C-C′ The the of the binding a of the C-C′ The of the the in a conformational binding conformational a shows a of the structure and the The in a conformational are with for the and for the and show the of the and are and are The C-C′ in the structure in with a the binding a and with a in the binding of a in this loop, in the loop, and that it the loop, and the of the and the structure the C-C′ a a in to the binding the glycan the region a conformational the a into a and the in the and the to a a a this of the binding this conformational it to the group and the to the this of ganglioside binding the of binding of to with and with the of to The in of The the and in to that the group a in the binding of the of that this sialic are of and a of the binding of and a of with the The with the and a interactions interactions are in The in a the sialic acid and the of the are of and of interactions with the and and The of the sialic acid the and the a in are with the with and with the binding in a The sialic acid the of with the key the sialic acid and the group of of this of the binding the sialic acid with the sialic acid with it the binding with Siglec-7 to of the and are and the and the of The with Siglec-7 with a The of the for the with in with the of the a with the and the and a the and group of in the C-C′ loop, a region with to for Siglec-7 group in a and the of CD33-related siglecs the that the are The in in the of CD33-related siglecs this the to in and to the of the of structural the the a the of recognition of the reveals that sialylated of are and are acid are and a with the in the and The with the glycan of the the of GT1b. of and binding in are with glycans. in this the the crystal structure of Siglec-7 the with the glycan a complex with the core the ligands and in are are in of the the of with and shows that the to the of the and the of the The shows in conformational to a that the of in the of and in crystal a and of the ligands that to have a the glycan are the of in the group and the of a of a of a of the and that a the to the underlying that are for and a the and the in the to the the of the and the for in a of the sialic acid shows that a the in the the the of a The of the the of ligands that with the it in the the glycan structural the in the of the and the and in the region in the the that this as the of this in the conformational in the of the the of the Siglec-7 crystal the C-C′ that this the structure the C-C′ with a Siglec-7 crystal to and and crystal the in the C-C′ the C-C′ loop, the of in the complex the of the C-C′ loop, the of the and to with the of GT1b. The of the The of the with in of a the C-C′ and a of and conformational the binding of the in the of the loop, a and that with the group a to a and the a to and the of the The of the of to to the of the to interact with the of this group the to interact in a it to this with the ganglioside in to the of ganglioside in the to the with oligosaccharide studies that Siglec-7 binds and with and the oligosaccharide a for in the for The for for the and for that the of the the binding and that the group in a of the that to a of that the in the binding of to to the to the to for binding to ganglioside a of of and interactions with the to the to GT1b. of to interact with the in binding it that the binding interactions sialylated in binding of to into for binding the with and to the of the are of in of the C-C′ with the to the of this the interactions of to that this for the binding of GT1b. shows binding in that to the of the glycan of the that to a of the C-C′ loop, the binding of the the are in ligands for have that expressed and expressed that Siglec-7 a ligands as of and a that of the of complex The of Siglec-7 important in the ganglioside the and complex the of Siglec-7 ligands complex to of and in and interactions with ligands Siglec-7 to interact in with ligands and interactions important for that α(2,8)-disialylated ligands to this with to to a crystal complex of Siglec-7 in complex with a ganglioside. to Siglec-7 with of the in a group the of the the of the to a to The of with this group it to and to The Siglec-7 complex a first glimpse how siglecs interact with of the complex that of the in the binding and that a conformational The sialic acid with the and a with The sialic acid a with and a with of to binding to with the sialic and with the the The of the glycan the C-C′ loop, a loop, it to interact with the conformational in the the of the the and a that this region important for the of the the of a previous that Siglec-7 and Siglec-7 and are binding to show that the of the C-C′ of Siglec-7 to with of binding a region the C-C′ loop, and the of the to of in for of Siglec-7 of region in the of with of Siglec-7 in binding We this region as in in the structure of it with the with this a The the siglecs in a acid in this the in Siglec-7 it the binding and and the of sialic acid to the it as it the of that the region of Siglec-7 in ganglioside binding with the C-C′ of for this Siglec-7 that the of the Siglec-7 binding The to and of in the to binding are a of and studies have that the to and that lectins have to a of lectins a of ligands for glycan in lectins to the glycan in a and the glycan structure with that of a structure to conformational the The a core of to The in the are to that the to binding group and the are the a of the of Siglec-7 to have binding for the gangliosides. in studies in a in binding in the the are to and the of the and are in a for the binding of family key to the ligands interact with in the of crystal structure shows that Siglec-7 for interactions with the ganglioside a conformational in the C-C′ loop, the and of the binding The of in the C-C′ and the have a the of the binding binding specificity, and binding studies with CD33-related are a group of receptors that the of the family sialic a that the of of sialylated ligands siglecs to and in the immune and the of in the and expressed siglec to to of the and immune siglecs have in of to the CD33-related siglec and and the immune the of the to The siglec sialic acid binding in the a that a with the sialic acid the binding the sialic the underlying glycan core key to siglec binding The binding preference for siglecs the and and glycan the in are for siglec binding are that of a to a sialylated a core the of neutral and sialic acid in of sialic acid Siglec-7 expressed and to a and a of binding studies have that Siglec-7 shows a preference for acid and sialic acid The acid in as and have that a expressed to interactions with Siglec-7 expressed to the of the and in the and a have the structure of Siglec-7 as a template for the CD33-related siglec and the of binding for the sialic acid We the crystal structure of Siglec-7 in complex with a ganglioside structure reveals for the first how Siglec-7 with a complex oligosaccharide to a dramatic conformational in the of the the and of Siglec-7 of the Siglec-7 The expressed as a a The a and with The with to a of and the to of of for a in and to and with a of the with and in and and with a of to the and and the of the Siglec-7 structure with of and of of the in with in and and of the and the group of the into in the binding and The of and of with in the and of the for and of in a and of the a in a The into The for a in and the and and and the binding with of ganglioside in and to The in and with in with a of for and to the a the the with of to and and a with ganglioside in the of the oligosaccharide for the to of the the and of Siglec-7 of the Siglec-7 The expressed as a a The a and with The with to a of and the to of of for a in and to and with a of the with and in and and with a of to the and and the of the Siglec-7 structure with of and of of the in with in and and of the and the group of the into in the binding and The of and of with in the and of the for and of the a in a The into The for a in and the and and and the binding with of ganglioside in and to The in and with in with a of for and to the a the the with of to and and a with ganglioside in the of the oligosaccharide for the to Siglec-7 expressed as a The a structure that Siglec-7 co-crystallized with a in a group the The complex in a as to the with the and the complex The structure to with and structure of as that a and The glycan binding the in the binding for the allowing and the group to of the of the are in the the sialic acid of the of the binding reveals that the the of the binding the sialic the binding this and the a the C-C′ and the of the the of the binding and the C-C′ The the of the binding a of the C-C′ The of the the in a and a of the binding of and a of with the The with the and a interactions interactions are in The in a the sialic acid and the of the are of and of interactions with the and and The of the sialic acid the and the a in are with the with and with the binding in a The sialic acid the of with the key the sialic acid and the group of of this of the binding the sialic acid with the sialic acid with it the binding with Siglec-7 to of the and are and the and the of The with Siglec-7 with a The of the for the with in with the of the a with the and the and a the and group of in the C-C′ loop, a region with to for Siglec-7 group in a and the of CD33-related siglecs the that the are The in in the of CD33-related siglecs this the to in and to the of the of structural the the a the of recognition of the reveals that sialylated of are and are acid are and a with the in the and The with the glycan of the the of GT1b. of and binding in are with glycans. in this the the crystal structure of Siglec-7 the with the glycan a complex with the core the ligands and in are are in of the the of with and shows that the to the of the and the of the The shows in conformational to a that the of in the of and in crystal a and of the ligands that to have a the glycan are the of in the group and the of a of a of a of the and that a the to the underlying that are for and a the and the in the to the the of the and the for in a of the sialic acid shows that a the in the the the of a The of the the of ligands that with the it in the the glycan structural the in the of the and the and in the region in the the that this as the of this in the conformational in the of the the of the Siglec-7 crystal the C-C′ that this the structure the C-C′ with a Siglec-7 crystal to and and crystal the in the C-C′ the C-C′ loop, the of in the complex the of the C-C′ loop, the of the and to with the of GT1b. The of the The of the with in of a the C-C′ and a of and conformational the binding of the in the of the loop, a and that with the group a to a and the a to and the of the The of the of to to the of the to interact with the of this group the to interact in a it to this with the ganglioside in to the of ganglioside in the to the with oligosaccharide studies that Siglec-7 binds and with and the oligosaccharide a for in the for The for for the and for that the of the the binding and that the group in a of the that to a of that the in the binding of to to the to the to for binding to ganglioside a of of and interactions with the to the to GT1b. of to interact with the in binding it that the binding interactions sialylated in binding of to into for binding the with and to the of the are of in of the C-C′ with the to the of this the interactions of to that this for the binding of GT1b. shows binding in that to the of the glycan of the that to a of the C-C′ loop, the binding of the Siglec-7 expressed as a The a structure that Siglec-7 co-crystallized with a in a group the The complex in a as to the with the and the complex The structure to with and The structure of as that a and The glycan binding the in the binding for the allowing and the group to of the of the are in the the sialic acid of the of the binding reveals that the the of the binding the sialic the binding this and the a the C-C′ and the of the the of the binding and the C-C′ The the of the binding a of the C-C′ The of the the in a and a of the binding of and a of with the The with the and a interactions interactions are in The in a the sialic acid and the of the are of and of interactions with the and and The of the sialic acid the and the a in are with the with and with The sialic acid the of with the key the sialic acid and the group of of this of the binding the sialic acid with the The sialic acid with it the binding with Siglec-7 to of the and are and the and the of The with Siglec-7 with a The of the for the with in with the of the a with the and the and a the and group of in the C-C′ loop, a region with to for Siglec-7 The group in a and the of CD33-related siglecs the that the are The in in the of CD33-related siglecs this the to in and to the of the of structural the the a the of recognition of the reveals that sialylated of are and are acid are and a with the in the and The with the glycan of the the of GT1b. of and binding in are The of and in crystal a and of the ligands that to have a the glycan are the of in the group and the of a The of a of a of the and that a the to the underlying that are for and a the and the in the to the the of the and the of the sialic acid shows that a the in the the the of a The of the the of ligands that with the it in the the glycan structural the in the of the and the and in the region in the the that this as the of this in the conformational in the of the the of the Siglec-7 crystal the C-C′ that this the structure the C-C′ with a Siglec-7 crystal to and and crystal the in the C-C′ the C-C′ loop, the of in the complex the of the C-C′ loop, the of the and to with the of GT1b. The of the The of the with in of a the C-C′ and a of and conformational the binding of the in the of the loop, a and that with the group a to a and the a to and the of the The of the of to to The the of the to interact with the of this group the to interact in a it to this with the ganglioside in to the of ganglioside in the to the with oligosaccharide studies that Siglec-7 binds and with and the oligosaccharide a for in the for The for for the and for that the of the the binding and that the group in a of the that to a of that the in the binding of to to the to the to The for binding to ganglioside a of of and interactions with the to the to GT1b. of to interact with the in binding it that the binding interactions sialylated in of the C-C′ with the to the of this the interactions of to that this for the binding of GT1b. shows binding in that to the of the glycan of the that to a of the C-C′ loop, the binding of the the are in ligands for have that expressed and expressed that Siglec-7 a ligands as of and a that of the of complex The of Siglec-7 important in the ganglioside the and complex the of Siglec-7 ligands complex to of and in and interactions with ligands Siglec-7 to interact in with ligands and interactions important for that α(2,8)-disialylated ligands to this with to to a crystal complex of Siglec-7 in complex with a ganglioside. to Siglec-7 with of the in a group the of the the of the to a to The of with this group it to and to The Siglec-7 complex a first glimpse how siglecs interact with of the complex that of the in the binding and that a conformational The sialic acid with the and a with The sialic acid a with and a with of to binding to with the sialic and with the the The of the glycan the C-C′ loop, a loop, it to interact with the conformational in the the of the the and a that this region important for the of the the of a previous that Siglec-7 and Siglec-7 and are binding to show that the of the C-C′ of Siglec-7 to with of binding a region the C-C′ loop, and the of the to of in for of Siglec-7 of region in the of with of Siglec-7 in binding We this region as in in the structure of it with the with this a The the siglecs in a acid in this the in Siglec-7 it the binding and and the of sialic acid to the it as it the of that the region of Siglec-7 in ganglioside binding with the C-C′ of for this Siglec-7 that the of the Siglec-7 binding The to and of in the to binding are a of and studies have that the to and that lectins have to a of lectins a of ligands for glycan in lectins to the glycan in a and the glycan structure with that of a structure to conformational the The a core of to The in the are to that the to binding group and the are the a of the of Siglec-7 to have binding for the gangliosides. in studies in a in binding in the the are to and the of the and are in a for the binding of family key to the ligands interact with in the of crystal structure shows that Siglec-7 for interactions with the ganglioside a conformational in the C-C′ loop, the and of the binding The of in the C-C′ and the have a the of the binding binding specificity, and binding studies with CD33-related The the are in ligands for have that expressed and expressed that Siglec-7 a ligands as of and a that of the of complex The of Siglec-7 important in the ganglioside the and complex the of Siglec-7 ligands complex to of and in and interactions with ligands Siglec-7 to interact in with ligands and interactions important for that α(2,8)-disialylated ligands to this with to to a crystal complex of Siglec-7 in complex with a ganglioside. to Siglec-7 with of the in a group the of the the of the to a to The of with this group it to and to The Siglec-7 complex a first glimpse how siglecs interact with gangliosides. of the complex that of the in the binding and that a conformational The sialic acid with the and a with The sialic acid a with and a with of to binding to with the sialic and with the the The of the glycan the C-C′ loop, a loop, it to interact with the conformational in the the of the the and a that this region important for the of the ganglioside. the of a previous that Siglec-7 and Siglec-7 and are binding to show that the of the C-C′ of Siglec-7 to with of binding a region the C-C′ loop, and the of the to of in for of Siglec-7 of region in the of with of Siglec-7 in binding We this region as in in the structure of it with the with this a The the siglecs in a acid in this the in Siglec-7 it the binding and and the of sialic acid to the it as it the of The that the region of Siglec-7 in ganglioside binding with the C-C′ of for this Siglec-7 that the of the Siglec-7 binding The to and of in the to binding are a of and studies have that the to and that lectins have to a of lectins a of ligands for glycan in lectins to the glycan in a and the glycan structure with that of a structure to conformational the The a core of to The in the are to that the to binding group and the are the a of the of Siglec-7 to have binding for the gangliosides. in studies in a in binding in the the are to and the of the and are in a for the binding of family key to the ligands interact with in the of crystal structure shows that Siglec-7 for interactions with the ganglioside a conformational in the C-C′ loop, the and of the binding The of in the C-C′ and the have a the of the binding binding specificity, and binding studies with CD33-related We are for the the The for the oligosaccharide in