Collagen_mid is the conserved central region of bacterial collagen triple helix repeat proteins.

1: Streptococcus pyogenes sclB encodes a putative hypervariable surface protein with a collagen-like repetitive structure. Whatmore AM; Microbiology. 2001;147:419-429. PMID:11158359

2: Characterisation of a large family of polymorphic collagen-like proteins in the endospore-forming bacterium Pasteuria ramosa. McElroy K, Mouton L, Du Pasquier L, Qi W, Ebert D; Res Microbiol. 2011;162:701-714. PMID:21726633