Using Integrated Bioinformatics Strategy to Identify Critical Factors for the Structural Integrity of Salmonella T3SS

Type-III secretion system of Gram-negative bacteria is the major molecular machine responsible for the infection of host cells and the in-host survival of the bacteria. The T3SS is composed of three structural components: basal body, needle, and export apparatus. The needle is an extracellular protein complex that recognizes host cells and transport bacterial effector proteins into the host cells. The basal body forms a channel across the bacterial membranes and also provides structural support to the needle. The export apparatus selects effector proteins and initiates the transportation of these proteins. Since all these three structural components are formed by specific proteins, abolishing the interaction of these proteins will disrupt the structural integrity of one or more structural components of T3SS, and eventually affect the infection and/or virulence of the bacteria. In this study, we analyzed the sequential, structural, and interactomic features of Salmonella T3SS structural proteins. We found that these structural proteins have abundant short and/or long disordered regions that overlap with other structured/functional regions. We identified critical interaction patterns and hub proteins SipB, SpaO, and SpaS, in the interactome of T3SS structural proteins. We also predicted novel binding motifs for six T3SS structural proteins of which the interaction partners are unknown. These results are expected to shed light on future studies in the fields of T3SS structural integrity and drug discovery.