This is the first domain in this unusual penicillin-binding protein PBP), Tp47 is mainly composed of beta-strands and is sequentially non-contiguous. The first three domains in Tp47 interact with each other through intimate domain-domain interfaces. Domain A contacts domain B through its N-terminal segment. Domain A also interacts tightly with domain C, Tp47 is unusual in that it displays beta-lactamase activity, and thus it does not fit the classical structural and mechanistic paradigms for PBPs, and thus Tp47 appears to represent a new class of PBP [1].

1: Crystal structure of the 47-kDa lipoprotein of Treponema pallidum reveals a novel penicillin-binding protein. Deka RK, Machius M, Norgard MV, Tomchick DR; J Biol Chem. 2002;277:41857-41864. PMID:12196546