Might function as an adhesin for host (human) cells. Cell surface Apa binds to human PSP-A (SFTPA1) via its glycosylated sites where it might down-regulate the immune response; PSP-A probably binds other bacterial proteins as well (PubMed:17158455). Binds to human PSP-A (SFTPA1) via its glycosylated moiety; binding disappears after treatment with alpha-mannosidase (PubMed:17158455). Glycosylated (PubMed:17158455). Runs as 45 and 47 kDa protein, the nature of the difference between the 2 forms is not known (PubMed:8423100, PubMed:17158455). Belongs to the Apa family.