Staphylococcus aureus Operates Protein-tyrosine Phosphorylation through a Specific Mechanism

Didier Soulat,Bertrand Duclos,Alain J Cozzone,Jean-Michel Jault,Christophe Geourjon,Christophe Grangeasse

doi:10.1074/jbc.m513600200

Abstract

Protein phosphorylation on tyrosine has been originally characterized in animal systems and has been shown to be involved in several fundamental processes including signal transduction, growth control, and malignancy. It has been later demonstrated to occur also in a number of bacteria, and recent data suggest that it may participate in the control of bacterial pathogenicity. In this work, we provide evidence that the gram-positive human pathogen Staphylococcus aureus harbors a protein-tyrosine kinase activity. This activity is borne by a protein, termed Cap5B2, whose phosphorylating capacity is expressed only in the presence of a stimulatory protein, either Cap5A1 or Cap5A2, that enhances its affinity for the phosphoryl donor ATP. In fact, the last 27/29 amino acids of the C-terminal domain of either polypeptide are sufficient for stimulating Cap5B2 activity. The stimulation of Cap5B2 by Cap5A1 involves essentially three amino acid residues in a helix of Cap5A1 (Asp202, Glu203, and Asp205) and three residues in a helix (helix 7) of Cap5B2 (Glu190, Lys192, and Lys193), thus suggesting helix-helix interaction between these two proteins. This type of helix-helix interaction resembles the interaction required for the activation of MinD ATPase by MinE protein in the process of septum-site determination, MinD sharing sequence similarity with Cap5B2. Such activation mechanism is described here in a gram-positive bacterial tyrosine kinase, and differs from the activation mechanism previously proposed for gram-negative bacteria. Therefore, it appears that S. aureus, and possibly other gram-positive bacteria, utilizes a specific molecular mechanism for triggering protein-tyrosine kinase activity.

Highlights

When comparing prokaryotes to eukaryotes in terms of protein-tyrosine phosphorylation, it appears that the overall reaction of phosphorylation is identical in both classes of organisms in the sense that the enzymes involved, protein-tyrosine kinases, can autophosphorylate on multiple tyrosine residues, or phosphorylate other protein substrates on tyrosine, at the expense of ATP as the phosphoryl donor
In the case of S. aureus serotype 5, the A1 and A2 polypeptides are located in the membrane, whereas B1 and B2 are in the cytoplasmic fraction (Fig. 1)
A major well established difference concerns the existence of two separate polypeptides in Grampositive bacteria, instead of only one in Gram-negative cells, that are needed for triggering tyrosine phosphorylation activity

Summary

This study This study

S. aureus genome analysis reveals two couples of polypeptides harboring a putative tyrosine kinase activity, the Cap5A1/Cap5B1 ( termed A1/B1) and the Cap5A2/Cap5B2 ( termed A2/B2). In terms of biological role, A1 and B1 are thought to function together as a polysaccharide co-polymerase and because of their respective sequence similarity, A2 and B2 are supposed to have a similar activity. The tyrosine phosphorylating activity of A1/B1 and A2/B2 has been biochemically characterized and the amino acid sequences needed for this activity have been determined, leading to a molecular model based on specific protein-protein interaction required for the kinase activity Such protein-protein interaction is reminiscent of a mechanism found in the MinD/MinE interaction required for the process of septum site determination

EXPERIMENTAL PROCEDURES

RESULTS

DISCUSSION