Characterization and Solution Structure of Mouse Myristoylated Methionine Sulfoxide Reductase A

Bart Ghesquière,Geumsoo Kim,Grzegorz Piszczek,Rodney L. Levine,Nico Tjandra,Jung Chae Lim,James M. Gruschus

doi:10.1074/jbc.m112.368936

Abstract

Methionine sulfoxide reductase A is an essential enzyme in the antioxidant system which scavenges reactive oxygen species through cyclic oxidation and reduction of methionine and methionine sulfoxide. The cytosolic form of the enzyme is myristoylated, but it is not known to translocate to membranes, and the function of myristoylation is not established. We compared the biochemical and biophysical properties of myristoylated and nonmyristoylated mouse methionine sulfoxide reductase A. These were almost identical for both forms of the enzyme, except that the myristoylated form reduced methionine sulfoxide in protein much faster than the nonmyristoylated form. We determined the solution structure of the myristoylated protein and found that the myristoyl group lies in a relatively surface exposed "myristoyl nest." We propose that this structure functions to enhance protein-protein interaction.

Highlights

Mammalian methionine sulfoxide is myristoylated, but the function of myristoylation is unknown
The cytosolic form is myristoylated on its amino-terminal residue, Gly-22.3 Myristoylation is required for membrane binding of certain proteins, but it is not sufficient to direct them to the membrane [7]
To probe for effects of myristoylation on secondary structure or conformational dynamics, we examined the tryptophan fluorescence and thermal stability of the two forms of msrA

Summary

Background

Mammalian methionine sulfoxide is myristoylated, but the function of myristoylation is unknown. Methionine sulfoxide reductase A is an essential enzyme in the antioxidant system which scavenges reactive oxygen species through cyclic oxidation and reduction of methionine and methionine sulfoxide. We determined the solution structure of the myristoylated protein and found that the myristoyl group lies in a relatively surface exposed “myristoyl nest.” We propose that this structure functions to enhance protein-protein interaction. Repair systems have evolved for the reversible modifications, including oxidation and reduction of the sulfur-containing amino acids cysteine and methionine. The latter is relatively readily oxidized to methionine sulfoxide. Myristoylated Methionine Sulfoxide Reductase A tion, we carried out biochemical, biophysical, and structural studies of the myristoylated and nonmyristoylated mouse cytosolic msrA

EXPERIMENTAL PROCEDURES

RESULTS

DISCUSSION