Characterization of the methionine sulfoxide reductase activities of PILB, a probable virulence factor from Neisseria meningitidis.
PILB has been described as being involved in the virulence of bacteria of Neisseria genus. The PILB protein is composed of three subdomains. In the present study, the central subdomain (PILB-MsrA), the C terminus subdomain (PILB-MsrB), and the fused subdomain (PILB-MsrA/MsrB) of N. meningitidis were produced as folded entities. The central subdomain shows a methionine sulfoxide reductase A (MsrA) activity, whereas PILB-MsrB displays a methionine sulfoxide reductase B (MsrB) activity. The catalytic mechanism of PILB-MsrB can be divided into two steps: 1) an attack of the Cys-494 on the sulfur atom of the sulfoxide substrate, leading to formation of a sulfenic acid intermediate and release of 1 mol of methionine/mol of enzyme and 2) a regeneration of Cys-494 via formation of an intradisulfide bond with Cys-439 followed by reduction with thioredoxin. The study also shows that 1) MsrA and MsrB display opposite stereoselectivities toward the sulfoxide function; 2) the active sites of both Msrs, particularly MsrB, are rather adapted for binding protein-bound MetSO more efficiently than free MetSO; 3) the carbon Calpha is not a determining factor for efficient binding to both Msrs; and 4) the presence of the sulfoxide function is a prerequisite for binding to Msrs. The fact that the two Msrs exhibit opposite stereoselectivities argues for a structure of the active site of MsrBs different from that of MsrAs. This is further supported by the absence of sequence homology between the two Msrs in particular around the cysteine that is involved in formation of the sulfenic acid derivative. The fact that the catalytic mechanism takes place through formation of a sulfenic acid intermediate for both Msrs supports the idea that sulfenic acid chemistry is a general feature in the reduction of sulfoxides by thiols.
Olry
Alexandre
A
UMR CNRS-UHP 7567, Maturation des ARN et Enzymologie Moléculaire, Faculté des Sciences, Blvd. des Aiguillettes, BP 239, Vandoeuvre-les-Nancy 54506, France.
Boschi-Muller
Sandrine
S
Marraud
Michel
M
Sanglier-Cianferani
Sarah
S
Van Dorsselear
Alain
A
Branlant
Guy
G
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000378:metabolism*; D001665:Binding Sites; D002384:Catalysis; D003545:Cysteine / Q000737:chemistry; D004220:Disulfides; D007700:Kinetics; D013058:Mass Spectrometry; D008715:Methionine / Q000378:metabolism; D051150:Methionine Sulfoxide Reductases; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009345:Neisseria meningitidis / Q000201:enzymology* / Q000472:pathogenicity; D010088:Oxidoreductases / Q000737:chemistry* / Q000378:metabolism*; D010957:Plasmids / Q000378:metabolism; D011485:Protein Binding; D011487:Protein Conformation; D017510:Protein Folding; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid; D012694:Serine / Q000737:chemistry; D013053:Spectrophotometry; D013434:Sulfenic Acids / Q000378:metabolism; D013879:Thioredoxins / Q000378:metabolism
D001426:Bacterial Proteins; D004220:Disulfides; D013434:Sulfenic Acids; D012694:Serine; D013879:Thioredoxins; D008715:Methionine; D010088:Oxidoreductases; D051150:Methionine Sulfoxide Reductases; C027219:methionine sulfoxide reductase; C068255:pilB protein, Bacteria; D003545:Cysteine