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Protein phosphorylation in Mycoplasma gallisepticum
M W Platt1, S Rottem, Y Milner
1Department of Membrane and Ultrastructure Research, Hebrew University-Hadassah Medical School, Jerusalem, Israel.
European Journal of Biochemistry
|September 1, 1988
Summary
Mycoplasma gallisepticum possesses a reversible protein phosphorylation system. A 55-kDa protein is phosphorylated on serine, regulated by specific divalent cations and a phosphatase.
Area of Science:
- Microbiology
- Molecular Biology
- Biochemistry
Background:
- Mycoplasma gallisepticum is a significant avian pathogen.
- Reversible protein phosphorylation is a key regulatory mechanism in cellular processes.
- Understanding Mycoplasma gallisepticum's molecular mechanisms is crucial for disease control.
Purpose of the Study:
- To investigate protein phosphorylation in Mycoplasma gallisepticum.
- To identify the primary protein substrate and characterize the associated kinase and phosphatase activities.
Main Methods:
- In vitro phosphorylation assays using [gamma-32P]ATP.
- Radiolabeling of intact cells with [32P]orthophosphate.
- Acid hydrolysis and 2D electrophoresis for phosphoprotein identification.
- Enzyme activity assays for kinase and phosphatase characterization.
Main Results:
- A 55-kDa protein is the major endogenous substrate, accepting >95% of phosphate.
- Phosphorylation occurs on serine residues.
- The phosphorylation is optimal at pH 5.5-6.0, requiring Ca2+ and Zn2+.
- A reversible phosphoprotein phosphatase with optimal activity at pH 7.5-8.0 was identified.
- The phosphatase is modulated by inorganic phosphate, arsenate, pyrophosphate, ATP, and ADP.
Conclusions:
- Mycoplasma gallisepticum exhibits a regulated, reversible protein phosphorylation system centered on a 55-kDa phosphoserine protein.
- This system is influenced by specific divalent cations and phosphatase modulators.
- The reversible phosphorylation may play a role in cell shape and gliding motility.