Unveiling a trans-4-hydroxy-L-proline substrate binding protein in Vibrio spp.

Abstract

Free trans -4-hydroxy-L-proline (T4LHyp), primarily released during the natural degradation of collagen, is absorbed and catabolised by heterotrophic bacteria, contributing to the global recycling of carbon and nitrogen. While bacterial T4LHyp catabolism is well documented, our understanding on how bacteria recognize and import T4LHyp remains limited. Here we show that HatA, the substrate binding protein (SBP) of an ATP-binding cassette transporter within the T4LHyp gene cluster of Vibrio alginolyticus 1A11092, recognizes T4LHyp during its uptake by the strain. HatA possessed significant binding affinity towards T4LHyp and L-proline and a binding signature (W 33 F 37 D 86 V 135 F 240 R 243 Y 265 N 267 Y 303 ), acting as the structural determinant for the specific ligand recognition, was defined. This signature is strictly conserved among HatA and its homologs, representing a subgroup of cluster D-II of SBPs. Genes encoding HatA-like SBPs are often located adjacent to collagenase and T4LHyp catabolic enzyme genes, and are nearly exclusively found in the genomes of Vibrio spp. in hosts and marine environments, which helps them exert pathogenicity when encountering host or environmental collagen. This study reveals a T4LHyp SBP in cosmopolitan Vibrio spp., offering better insights into the global T4LHyp catabolism and recycling driven by bacteria.