The collagens are a family of animal proteins containing segments of repeated Gly-Xaa-Yaa
(GXY) motifs that form a characteristic triple-helical structure. Genes encoding proteins with
repeated GXY motifs have also been reported in bacteria and phages; however, it is unclear
whether these prokaryotic proteins can form a collagen-like triple-helical structure. Here we
used two recently identified streptococcal proteins, Scl1 and Scl2, containing extended GXY
sequence repeats as model proteins. First we observed that prior to heat denaturation …