Structure and Function Analysis of Microcystin Transport Protein MlrD.

Abstract

Microorganisms play a crucial role in the degradation of microcystins (MCs), with most MC-degrading bacteria utilizing the mlr gene cluster (mlrABCD) mechanism. While previous studies have advanced our understanding of the structure, function, and degradation mechanisms of MlrA, MlrB, and MlrC, research on MlrD remains limited. Consequently, the molecular structure and specific catalytic processes of MlrD are still unclear. This study investigates MlrD from Sphingopyxis sp. USTB-05, utilizing bioinformatics tools for analysis and prediction, conducting homology analysis, and constructing the molecular structure of MlrD. Bioinformatics analysis suggests that MlrD is an alkaline, hydrophobic protein with good thermal stability and is likely located in the cell membrane as a membrane protein without a signal peptide. Homology analysis indicates that MlrD belongs to the PTR2 protein family and contains a PTR2 domain. Phylogenetic analysis reveals that MlrD follows both vertical and horizontal genetic transfer patterns during evolution. Homology modeling demonstrates that the three-dimensional structure of MlrD is primarily composed of 12 α-helices, with conserved residues between the N-terminal and C-terminal domains forming a large reaction cavity. This research broadens current knowledge of MC biodegradation and offers a promising foundation for future studies.