PNNL

Abstract

Human gut commensal Bacteroidetes rely on multiple transport systems to acquire vitamin B12 and related cobamides for fitness in the gut. In addition to a set of conserved transport proteins, these systems also include a diverse and heterogeneous repertoire of additional proteins with unknown function. Here we report the function and structural characterization of one of these proteins, BtuH, which binds vitamin B12 directly via a 24 C-terminal globular domain that has no known structural homologs. This protein is required for efficient B12 transport and competitive fitness in the gut, demonstrating that members of the heterogenous suite of accessory proteins encoded in Bacteroides cobamide transport system loci can play key roles in vitamin acquisition.