OspB

Outer surface proteins A and B (Osp1A and OspB) are basic lipoproteins encoded by a single operon located on a 54-kb linear plasmid of the B. burgdorferi genome. Both are abundant in cultured organisms. OspB (31 kDa, apparent size 34 kDa by SDS-PAGE) has 53% sequence identity to OspA (28 kDa, apparent size 31 kDa by SDS-PAGE). The N termini of both proteins are lipidated following signal peptide cleavage. The structure of a recombinant, nonlipidated OspA has been determined in complexes with antigen-binding fragments (Fabs) of two different murine monoclonal antibodies . Both OspA and OspB are expressed by B. burgdorferi in infected unfed ticks, but are down-regulated during tick feeding. Recent studies suggest that both lipoproteins may play a role in B. burgdorferi colonization and survival within the tick. OspA and OspB may also be expressed in late stage human disease