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 Weisman, L. S. Articles by Ballou, C. E. Search for Related Content PubMed PubMed Citation Articles by Weisman, L. S. Articles by Ballou, C. E. Social Bookmarking                      What's this?

J. Biol. Chem., Vol. 259, Issue 6, 3464-3469, 03, 1984

Biosynthesis of the mycobacterial methylmannose polysaccharide. Identification of a 3-O-methyltransferase

LS Weisman and CE Ballou

The methylmannose polysaccharide (MMP), found in the cytoplasm of Mycobacterium smegmatis, is composed of 10 to 13 3-O-methylmannoses joined by alpha 1----4 linkages. Each molecule is terminated by an unmethylated mannose and the reducing end is blocked by an alpha-linked methyl aglycon. Two enzymes involved in MMP biosynthesis have been identified in cell extracts, an alpha 1----4 mannosyltransferase (described in the previous paper) and a 3-O-methyltransferase reported here. Studies of substrate specificity and characterization of the products formed demonstrate that MMP elongation occurs via sequential mannosylation and methylation. The 3-O-methyltransferase, unlike the mannosyltransferase, is readily solubilized. It catalyzes transfer of a methyl group from S-adenosylmethionine to position 3 of a terminal alpha 1----4-linked mannose. The labeled product formed from S-[methyl- 3H]adenosylmethionine and Man-MeMan5-OCH3 was characterized both by its resistance to periodate oxidation and by the release of labeled 3-O- methylmannose upon acid hydrolysis. Like the mannosyltransferase, the 3- O-methyltransferase utilizes shorter oligomeric acceptors preferentially. The Km values of the methyltransferase for Man-MeMan4- OCH3 and S-adenosylmethionine are 0.7 and 0.4 mM, respectively. Because MMP homologs isolated from the cell are terminated by an unmethylated mannose, the methyl-transferase appears to be responsible for MMP chain termination. Moreover, palmitoyl-CoA selectively inhibits methylation of Man-MeMan12-OCH3 when Man-MeMan4-OCH3 and Man-MeMan12-OCH3 are incubated together with the methyltransferase, which suggests that complex formation between the longer homologs and lipids may play a role in the termination process.
CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this?

This article has been cited by other articles:

				G. Stadthagen, T. Sambou, M. Guerin, N. Barilone, F. Boudou, J. Kordulakova, P. Charles, P. M. Alzari, A. Lemassu, M. Daffe, et al. Genetic Basis for the Biosynthesis of Methylglucose Lipopolysaccharides in Mycobacterium tuberculosis J. Biol. Chem., September 14, 2007; 282(37): 27270 - 27276. [Abstract] [Full Text] [PDF]

				R Blomhoff, M. Green, T Berg, and K. Norum Transport and storage of vitamin A Science, October 19, 1990; 250(4979): 399 - 404. [Abstract] [PDF]