Relationship between exopolysaccharide production and protein-tyrosine phosphorylation in gram-negative bacteria.
The phosphorylation of proteins at tyrosine residues is known to play a key role in the control of numerous fundamental processes in animal systems. In contrast, the biological significance of protein-tyrosine phosphorylation in bacteria, which has only been recognised recently, is still unclear. Here, we have analysed the role in Escherichia coli cells of an autophosphorylating protein-tyrosine kinase, Wzc, and a phosphotyrosine-protein phosphatase, Wzb, by performing knock-out experiments on the corresponding genes, wzc and wzb, and looking at the metabolic consequences induced. The results demonstrate that the phosphorylation of Wzc, as regulated by Wzb, is directly connected with the production of a particular capsular polysaccharide, colanic acid. Thus, when Wzc is phosphorylated on tyrosine, no colanic acid is synthesised by bacteria, but when dephosphorylated by Wzb, colanic acid is produced. This process is rather specific to the pair of proteins Wzc/Wzb. Indeed, a much lesser effect, if any, on colanic acid synthesis is observed when knock-out experiments are performed on another pair of genes, etk and etp, which also encode respectively a protein-tyrosine kinase, Etk, and a phosphotyrosine-protein phosphatase, Etp, in E. coli. In addition, the analysis of the phosphorylation reaction at the molecular level reveals differences between Gram-negative and Gram-positive bacteria, namely in the number of protein components required for this reaction to occur.
Vincent
C
C
Institute of Biology and Chemistry of Proteins, Centre National de la Recherche Scientifique, 7, Passage du Vercors, Lyon, 69007, France.
Duclos
B
B
Grangeasse
C
C
Vaganay
E
E
Riberty
M
M
Cozzone
A J
AJ
Doublet
P
P
D000595:Amino Acid Sequence; D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D017353:Gene Deletion; D006090:Gram-Negative Bacteria / Q000201:enzymology / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D006094:Gram-Positive Bacteria / Q000201:enzymology / Q000235:genetics / Q000378:metabolism; D008565:Membrane Proteins; D008969:Molecular Sequence Data; D010766:Phosphorylation; D019000:Phosphotyrosine / Q000378:metabolism*; D011134:Polysaccharides / Q000096:biosynthesis*; D017027:Protein Tyrosine Phosphatases / Q000235:genetics / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016415:Sequence Alignment; D013379:Substrate Specificity
D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D008565:Membrane Proteins; D011134:Polysaccharides; C417168:WZC protein, Bacteria; D019000:Phosphotyrosine; C004275:colanic acid; D011505:Protein-Tyrosine Kinases; C499615:wzc protein, E coli; D017027:Protein Tyrosine Phosphatases