This immunoglobulin-like domain is found in bacteria in the GldM protein. GldM, is named for the member from Cytophaga johnsonae (Flavobacterium johnsoniae), which is required for a type of rapid gliding motility found in certain members of the Bacteriodetes [1].

1: Flavobacterium johnsoniae gliding motility genes identified by mariner mutagenesis. Braun TF, Khubbar MK, Saffarini DA, McBride MJ; J Bacteriol. 2005;187:6943-6952. PMID:16199564

2: Type IX secretion system PorM and gliding machinery GldM form arches spanning the periplasmic space. Leone P, Roche J, Vincent MS, Tran QH, Desmyter A, Cascales E, Kellenberger C, Cambillau C, Roussel A; Nat Commun. 2018;9:429. PMID:29382829

3: PorM, a core component of bacterial type IX secretion system, forms a dimer with a unique kinked-rod shape. Sato K, Okada K, Nakayama K, Imada K; Biochem Biophys Res Commun. 2020;532:114-119. PMID:32828535