Mkp1 of Pneumocystis carinii associates with the yeast transcription factor Rlm1 via a mechanism independent of the activation state.
The mitogen-activated protein (MAP) kinase Mkp1 of the fungal pathogen Pneumocystis carinii is a functional MAP kinase that complements the loss of Slt2p, the MAP kinase component of the cell integrity pathway of Saccharomyces cerevisiae, and is activated within P. carinii in response to oxidative stress. Mkp1 displays an unusual feature in that it contains a phosphorylation motif repeat (TEYMTEY) within the activation loop not present in any other fungal MAPK identified to date. Mutagenesis of the T186,Y188 phosphorylation motif within the activation domain of Mkp1 results in the loss of detectable kinase activity but still retains partial complementation function. In addition to the ability of Mkp1 to restore partial activity to the cell integrity pathway in the absence of phosphorylatable residues within the activation loop, the association of Mkp1 with a substrate of Slt2p, the transcription factor Rlm1p, can also occur in the absence of MAP kinase activation. The results of this study suggest that the presence of phosphorylatable residues within the activation loop of Mkp1 is not absolutely required for functional (complementation) activity or for the association of Mkp1 with the transcription factor Rlm1p. In contrast, the catalytic lysine of the ATP-binding domain of Mkp1 is necessary for both complementation function and interaction with Rlm1p.
Fox
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Department of Pathology, University of Cincinnati College of Medicine, Cincinnati, OH 45267, USA.
Smulian
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AG
D000255:Adenosine Triphosphate / Q000378:metabolism; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D001665:Binding Sites; D004789:Enzyme Activation; D005656:Fungal Proteins / Q000378:metabolism*; D005816:Genetic Complementation Test; D026161:MADS Domain Proteins; D020928:Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010766:Phosphorylation; D011010:Pneumocystis / Q000201:enzymology*; D011487:Protein Conformation; D011499:Protein Processing, Post-Translational; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors / Q000378:metabolism*; D020798:Two-Hybrid System Techniques
D005656:Fungal Proteins; D026161:MADS Domain Proteins; C095725:RLM1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; D000255:Adenosine Triphosphate; D020928:Mitogen-Activated Protein Kinases; C072724:SLT2 protein, S cerevisiae