Ser6 in the maize actin‐depolymerizing factor, ZmADF3, is phosphorylated by a calcium‐stimulated protein kinase and is essential for the control of functional activity

• Published in: The Plant journal : for cell and molecular biology Vol. 14; no. 2; pp. 187 - 193
• Main Authors: Smertenko, Andrei P., Jiang, Chang‐Jie, Simmons, Nicola J., Weeds, Alan G., Davies, Dewi R., Hussey, Patrick J.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Science Ltd 01-04-1998; Blackwell Science
• Subjects: Actin Depolymerizing Factors; Actins - metabolism; Amino Acid Sequence; Biological and medical sciences; Calcium - physiology; Cell biochemistry; Cell physiology; Cell structures and functions; Cytoskeleton, cytoplasm. Intracellular movements; Destrin; Fundamental and applied biological sciences. Psychology; Gelsolin - metabolism; Kinetics; Microfilament Proteins - genetics; Microfilament Proteins - metabolism; Molecular and cellular biology; Molecular Sequence Data; Mutagenesis, Site-Directed; Phosphorylation; Plant Extracts - metabolism; Plant physiology and development; Protein Binding; Protein Kinases - metabolism; Recombinant Proteins - metabolism; Serine - metabolism; Zea mays - metabolism; Binding; Monocotyledones; Phosphorylation; Zea mays; Enzyme; Transferases; Microfilament; Structure function relationship; Protein; Signal transduction; Gramineae; Actin; Dynamics; Protein kinase; Angiospermae; Cytoskeleton; Spermatophyta
• ISSN: 0960-7412; 1365-313X
• DOI: 10.1046/j.1365-313X.1998.00107.x

Summary
Maize actin‐depolymerizing factor, ZmADF, binds both G‐ and F‐actin and enhances in vitro actin dynamics. Evidence from studies on vertebrate ADF/cofilin supports the view that this class of protein responds to intracellular and extracellular signals and causes actin reorganization. As a test to determine whether such signal‐responsive pathways existed in plants, this study addressed the ability of maize ADF to be phosphorylated and the likely effects of such phosphorylation on its capacity to modulate actin dynamics. It is shown that maize ADF3 (ZmADF3) can be phosphorylated by a calcium‐stimulated protein kinase present in a 40–70% ammonium sulphate fraction of a plant cell extract. Phosphorylation is shown to be on Ser6, which is only one of nine amino acids that are fully conserved among the ADF/cofilin proteins across distantly related species. In addition, an analogue of phosphorylated ZmADF3 created by mutating Ser6 to Asp6 (zmadf3–4) does not bind G‐ or F‐actin and has little effect on the enhancement of actin dynamics. These results are discussed in context of the previously observed actin reorganization in root hair cells.