This is a novel repeat in Pneumocystis carinii Major surface glycoprotein (MSG) some members of the alignment have up to nine repeats of this family, the repeats containing several conserved cysteines. The MSG of P. carinii is an important protein in host-pathogen interactions [2]. Surface glycoprotein A Swiss:O59920 from Pneumocystis carinii is a main target for the host immune system, this protein is implicated in the attachment of Pneumocystis carinii to the host alveolar epithelial cells, alveolar macrophages, host surfactant and possibly accounts in part for the hypoxia seen in Pneumocystis carinii pneumonia (PCP) [1].

1: Molecular characterization of mouse Pneumocystis carinii surface glycoprotein A. Haidaris CG, Medzihradsky OF, Gigliotti F, Simpson-Haidaris PJ; DNA Res 1998;5:77-85. PMID:9679195

2: Characterization of major surface glycoprotein genes of human Pneumocystis carinii and high-level expression of a conserved region. Mei Q, Turner RE, Sorial V, Klivington D, Angus CW, Kovacs JA; Infect Immun 1998;66:4268-4273. PMID:9712777