HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

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 PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Honig, G. R. Articles by Mason, R. G. Search for Related Content PubMed PubMed Citation Articles by Honig, G. R. Articles by Mason, R. G. Social Bookmarking                      What's this?

Unequal Synthesis of Complementary Globin Chains of Human Fetal Hemoglobin by the Effect of l-O-Methylthreonine

From the ¹ From the Department of Pediatrics, University of Illinois College of Medicine, Chicago, Illinois 60680

Incorporation of radioactive amino acids into the , ß, and chains of human hemoglobin was studied with erythroid cells from newborn infants. When the cells were incubated in isoleucine-free medium together with l-O-methylthreonine, which is an antagonist of l-isoleucine, inhibition of chain synthesis occurred. The concomitant synthesis of and ß chains, which do not contain isoleucine, was not significantly affected. Inhibition of chain synthesis by as much as 90% had virtually no effect on the synthesis of complementary chains, suggesting that the synthesis or release of chains does not require prior synthesis of these non- chains. As a result of the selective inhibition of synthesis of chains, cells incubated with the isoleucine antagonist synthesized a 2- to 3-fold excess of chains over the total non- chains. A major portion of the excess chains was present in the cell lysates uncombined with hemoglobin, and had Sephadex gel filtration properties consistent with their being present as dimers. When ß^a subunits were added to the lysates prior to Sephadex gel filtration, the excess chain radioactivity appeared in the hemoglobin fraction, suggesting that the free chains existed as completed globin-heme subunits which retained the capacity to combine with complementary subunits to form hemoglobin. When cells were incubated with l-O-methylthreonine and a radioactive amino acid in label-chase experiments, followed by 24-hour incubations, the excess radioactive chains remained in the soluble cell fraction. This was in contrast with reported studies with ß-thalassemia cells in which chain precipitation was demonstrated during cell incubations in vitro. This difference appeared to be the result of intracellular exchange of the radioactive chains with chains of preexisting hemoglobin in the cells incubated with l-O-methylthreonine, a reaction which may be undetectable in ß-thalassemia cells because of the presence of a preexisting pool of nonradioactive chains in these cells.

CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this?

This article has been cited by other articles:

				M. D. Hollenberg, M. M. Kaback, and H. H. Kazazian Jr. Adult Hemoglobin Synthesis by Reticulocytes from the Human Fetus at Midtrimester Science, November 12, 1971; 174(4010): 698 - 702. [Abstract] [PDF]

				M. Rabinovitz, M. L. Freedman, J. M. Fisher, and C. R. Maxwell Translational Control in Hemoglobin Synthesis Cold Spring Harb Symp Quant Biol, January 1, 1969; 34(0): 567 - 578. [Abstract] [PDF]