This family seems confined to Helicobacter. It is predicted to be an outer membrane protein based on its pattern of alternating hydrophobic amino acids similar to porins [1].

1: The complete genome sequence of the gastric pathogen Helicobacter pylori [see comments] [published erratum appears in Nature 1997 Sep 25;389(6649):412] Tomb JF, White O, Kerlavage AR, Clayton RA, Sutton GG, Fleischmann RD, Ketchum KA, Klenk HP, Gill S, Dougherty BA, Nelson K, Quackenbush J, Zhou L, Kirkness EF, Peterson S, Loftus B, Richardson D, Dodson R, Khalak HG, Glodek A, McKenney K, Fitzegerald LM, Nature 1997;388:539-547. PMID:9252185