Recycling or regulation? The role of amino-terminal modifying enzymes.
Post-translational modifications are essential for a variety of functions, such as the translocation, activation, regulation, and, ultimately, degradation of proteins. The amino-terminal (N-terminal) region is a particularly active area for such alterations. Three types of reactions predominate: limited proteolysis to remove one or more amino acids; modification of the alpha-amino group; and side-chain-specific changes. The N-terminal peptidases expose penultimate residues, providing new substrates for peptidase or transferase action. These enzymes can act sequentially or competitively to influence a protein's longevity, location or activity. N-terminal modifying enzymes (NTMEs) might target a protein for ubiquitination and degradation or protect a protein from rapid turnover. The N-terminal peptidases might also have important roles in processing the peptides that are released from the proteasome. Plant NTMEs have roles in senescence, meiosis and defense, and proposed roles in polar auxin transport.
Walling
Linda L
LL
Department of Botany and Plant Sciences, Center for Plant Cell Biology, University of California, Riverside, California 92521, USA. linda.walling@ucr.edu
D000626:Aminopeptidases / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental; D018506:Gene Expression Regulation, Plant; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D010944:Plants / Q000201:enzymology* / Q000235:genetics; D011499:Protein Processing, Post-Translational
D010940:Plant Proteins; D000626:Aminopeptidases