This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via CrossRef Citing Articles via Web of Science (47) Citing Articles via Google Scholar Google Scholar Articles by Chrispeels, M. J. Search for Related Content PubMed PubMed Citation Articles by Chrispeels, M. J. Agricola Articles by Chrispeels, M. J.

Articles

Synthesis and Secretion of Hydroxyproline-containing Macromolecules in Carrots

II. In vivo Conversion of Peptidyl Proline to Peptidyl Hydroxyproline

^a Department of Biology, John Muir College, University of California, San Diego, La Jolla, California 92037

The chelator ,'-dipyridyl prevents the formation of protein-bound hydroxyproline without affecting protein synthesis as measured by the incorporation of ¹⁴C-proline. The inhibitory effect can be overcome by exogenous ferrous ions. Neither ,'-dipyridyl nor Fe²⁺ interferes in any other known way with the synthesis and secretion of the hydroxyproline-rich proteins normally found in the cell wall. This reversal by Fe²⁺ of the inhibition of proline hydroxylation by ,'-dipyridyl is used for a study in vivo of the hydroxylation reaction. This reaction has a temperature coefficient of 2.2, suggesting that it is an enzymatic process. Reversal by Fe²⁺ of the ,'-dipyridyl inhibition can occur after protein synthesis has been arrested with cycloheximide, indicating that peptidyl proline is the substrate of the hydroxylation reaction. Hydroxylation occurs in the cytoplasm, and not in the cell wall, and only for a limited time after the incorporation of proline into the polypeptide chain. This suggests a spatial separation of the enzyme and the substrate.