5FA9 image
Entry Detail
PDB ID:
5FA9
Keywords:
Title:
Bifunctional Methionine Sulfoxide Reductase AB (MsrAB) from Treponema denticola
Biological Source:
Host Organism:
PDB Version:
Deposition Date:
2015-12-11
Release Date:
2016-09-14
Method Details:
Experimental Method:
Resolution:
2.30 Å
R-Value Free:
0.23
R-Value Work:
0.20
R-Value Observed:
0.20
Space Group:
C 1 2 1
Macromolecular Entities
Polymer Type:polypeptide(L)
Description:Peptide methionine sulfoxide reductase MsrA
Mutations:C11S, C285S
Chain IDs:A, B
Chain Length:325
Number of Molecules:2
Biological Source:Treponema denticola ATCC 35405
Primary Citation
Essential Role of the Linker Region in the Higher Catalytic Efficiency of a Bifunctional MsrA-MsrB Fusion Protein
Biochemistry 55 5117 5127 (2016)
PMID: 27551953 DOI: 10.1021/acs.biochem.6b00544

Abstact

Many bacteria, particularly pathogens, possess methionine sulfoxide reductase A (MsrA) and B (MsrB) as a fusion form (MsrAB). However, it is not clear why they possess a fusion MsrAB form rather than the separate enzymes that exist in most organisms. In this study, we performed biochemical and kinetic analyses of MsrAB from Treponema denticola (TdMsrAB), single-domain forms (TdMsrA and TdMsrB), and catalytic Cys mutants (TdMsrAB(C11S) and TdMsrAB(C285S)). We found that the catalytic efficiency of both MsrA and MsrB increased after fusion of the domains and that the linker region (iloop) that connects TdMsrA and TdMsrB is required for the higher catalytic efficiency of TdMsrAB. We also determined the crystal structure of TdMsrAB at 2.3 Å, showing that the iloop mainly interacts with TdMsrB via hydrogen bonds. Further kinetic analysis using the iloop mutants revealed that the iloop-TdMsrB interactions are critical to MsrB and MsrA activities. We also report the structure in which an oxidized form of dithiothreitol, an in vitro reductant for MsrA and MsrB, is present in the active site of TdMsrA. Collectively, the results of this study reveal an essential role of the iloop in maintaining the higher catalytic efficiency of the MsrAB fusion enzyme and provide a better understanding of why the MsrAB enzyme exists as a fused form.

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