Structural characterization of recombinant domain II of the basement membrane proteoglycan perlecan

Mouse perlecan domain II (325 residues), consisting of four cysteine-rich LA modules, one IG module and a link region, was obtained in purified form from a stably transfected mammalian cell clone. Rotary shadowing electron microscopy demonstrated a globular domain connected to a short rod-like segment of variable length. This suggested that tandem arrays of LA modules form rod-like elements. Folding into a native structure was indicated by the sharing of immunological epitopes with tissue perlecan, a CD spectrum demonstrating 37% beta structure and a limited susceptibility to proteolysis. The domain also showed N-glycosylation of a single acceptor site and 7-8 O-linked oligosaccharides. The latter were located mainly in the link region within proline-rich sequences.