This family contains many bacterial hypothetical proteins. The structures of Swiss:A1SD03, PDB:3hsa, and Swiss:A3QB43, PDB:3dcx, show similarities to the PH or pleckstrin homology domain. First evidence of PH-like domains in bacteria suggests role in cell envelope stress response [1].

1: Bacterial pleckstrin homology domains: a prokaryotic origin for the PH domain. Xu Q, Bateman A, Finn RD, Abdubek P, Astakhova T, Axelrod HL, Bakolitsa C, Carlton D, Chen C, Chiu HJ, Chiu M, Clayton T, Das D, Deller MC, Duan L, Ellrott K, Ernst D, Farr CL, Feuerhelm J, Grant JC, Grzechnik A, Han GW, Jaroszewski L, Jin KK, Klock HE, Knuth MW, Kozbial P, Krishna SS, Kumar A, Marciano D, McMullan D, Miller MD, Morse AT, Nigoghossian E, Nopakun A, Okach L, Puckett C, Reyes R, Rife CL, Sefcovic N, Tien HJ, Trame CB, van den Bedem H, Weekes D, Wooten T, Hodgson KO, Wooley J, Elsliger MA, Deacon AM, Godzik A, Lesley SA, Wilson IA. J Mol Biol. 2010 Feb 12;396(1):31-46. Epub 2009 Nov 10. PMID:19913036