UNIT 14.1 Overview of Protein Phosphorylation

  1. Bartholomew M. Sefton

Published Online: 1 MAY 2001

DOI: 10.1002/0471143030.cb1401s00

Current Protocols in Cell Biology

Current Protocols in Cell Biology

How to Cite

Sefton, B. M. 2001. Overview of Protein Phosphorylation. Current Protocols in Cell Biology. 00:14.1:14.1.1–14.1.3.

Author Information

  1. The Salk Institute, San Diego, California

Publication History

  1. Published Online: 1 MAY 2001
  2. Published Print: OCT 1998


Phosphorylation is the most common and important mechanism of acute and reversible regulation of protein function. Studies of mammalian cells metabolically labeled with [32P]orthophosphate suggest that as many as one-third of all cellular proteins are covalently modified by protein phosphorylation. Protein phosphorylation has an important role in essentially all aspects of cell biology. Most polypeptide growth factors (platelet-derived growth factor and epidermal growth factor are among the best studied) and cytokines (e.g., interleukin 2, colony stimulating factor 1, and γ-interferon) stimulate phosphorylation upon binding to their receptors. Induced phosphorylation in turn activates cytoplasmic protein kinases, such as Raf, the activators of the mitogen-activated protein (MAP) kinases SEK and MEK, the MAP kinases ERK, JNK, and p38, the Janus/JAK kinases, the p21 activated kinases (PAKs), and the phosphatidylinsoitil 3'-kinase-activated kinase, protein kinase B/Akt. Additionally, in all nucleated organisms, cell cycle progression is regulated at both the G1/S and the G2/M transitions by cyclin-dependent protein kinases. These kinases regulate the G1/S transition by the phosphorylation of cell cycle regulators such as Rb protein and the G2/M transition through the phosphorylation of nuclear lamins and histones.