Deciphering the function of an ORF: Salmonella enterica DeoM protein is a new mutarotase specific for deoxyribose.
We identified in Salmonella enterica serovar Typhi a cluster of four genes encoding a deoxyribokinase (DeoK), a putative permease (DeoP), a repressor (DeoQ), and an open reading frame encoding a 337 amino acid residues protein of unknown function. We show that the latter protein, called DeoM, is a hexamer whose synthesis is increased by a factor over 5 after induction with deoxyribose. The CD spectrum of the purified recombinant protein indicated a dominant contribution of betatype secondary structure and a small content of alpha-helix. Temperature and guanidinium hydrochloride induced denaturation of DeoM indicated that the hexamer dissociation and monomer unfolding are coupled processes. DeoM exhibits 12.5% and 15% sequence identity with galactose mutarotase from Lactococcus lactis and respectively Escherichia coli, which suggested that these three proteins share similar functions. Polarimetric experiments demonstrated that DeoM is a mutarotase with high specificity for deoxyribose. Site-directed mutagenesis of His183 in DeoM, corresponding to a catalytically active residue in GalM, yielded an almost inactive deoxyribose mutarotase. DeoM was crystallized and diffraction data collected for two crystal systems, confirmed its hexameric state. The possible role of the protein and of the entire gene cluster is discussed in connection with the energy metabolism of S. enterica under particular growth conditions.
Assairi
Liliane
L
Laboratoire de Chimie Structurale des Macromolécules, Unité de Recherche Associeé 2185 du Cantre National de la Recherche Scientifique, Institut Pasteur, 75724 Paris 15, France.
Bertrand
Thomas
T
Ferdinand
Joëlle
J
Slavova-Azmanova
Neli
N
Christensen
Mette
M
Briozzo
Pierre
P
Schaeffer
Francis
F
Craescu
Constantin T
CT
Neuhard
Jan
J
Bârzu
Octavian
O
Gilles
Anne-Marie
AM
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics* / Q000302:isolation & purification; D002238:Carbohydrate Epimerases / Q000737:chemistry* / Q000235:genetics* / Q000302:isolation & purification; D002942:Circular Dichroism; D003001:Cloning, Molecular; D003460:Crystallization; D018360:Crystallography, X-Ray; D003855:Deoxyribose / Q000737:chemistry / Q000378:metabolism*; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D016366:Open Reading Frames / Q000235:genetics; D019779:Salmonella enterica / Q000201:enzymology* / Q000235:genetics; D016415:Sequence Alignment; D013379:Substrate Specificity
D001426:Bacterial Proteins; D003855:Deoxyribose; D002238:Carbohydrate Epimerases; C019646:aldose 1-epimerase