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

J. Biol. Chem., Vol. 283, Issue 4, 1902-1910, January 25, 2008

This Article Full Text Full Text (PDF) All Versions of this Article: 283/4/1902    most recent M708593200v1 Submit a Letter to Editor Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map 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 Request Permissions Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Maytum, R. Articles by Geeves, M. A. Search for Related Content PubMed PubMed Citation Articles by Maytum, R. Articles by Geeves, M. A. Social Bookmarking                      What's this?

Ultra Short Yeast Tropomyosins Show Novel Myosin Regulation^*

Robin Maytum¹, Victoria Hatch, Manfred Konrad^¶, William Lehman, and Michael A. Geeves^||

From the School of Biological and Chemical Sciences, Queen Mary, University of London, E1 4NS, United Kingdom, the ^¶Max-Planck Institute for Biophysical Chemistry, Göttingen D-73070, Germany, the Department Physiology & Biophysics, Boston University, Boston, Massachusetts 02118, and the ^||Department of Biosciences, University of Kent, Canterbury CT2 7NJ, United Kingdom

Tropomyosin (Tm) is an -helical coiled-coil actin-binding protein present in all eukaryotes from yeast to man. Its functional role has been best described in muscle regulation; however its much wider role in cytoskeletal actin regulation is still to be clarified. Isoforms vary in size from 284 or 248 amino acids in vertebrates, to 199 and 161 amino acids in yeast, spanning from 7 to 4 actin binding sites respectively. In Saccharomyces cerevisiae, the larger yTm1 protein is produced by an internal 38-amino acid duplication, corresponding to a single actin-binding site. We have produced an ultra-short Tm with only 125 amino acids by removing both of the 38 amino acid repeats from yTm1, with the addition of an Ala-Ser extension used to mimic the essential N-terminal acetylation. This short Tm, and an M1T mutant of it, bind to actin with a similar affinity to most Tms previously studied (K_50% 0.5 µM). However, an equilibrium fluorescence binding assay shows a much greater inhibition of myosin binding to actin than any previously studied Tm. Actin cosedimentation assays show this is caused by direct competition for binding to actin. The M1T mutant shows a reduced inhibition, probably due to weaker end-to-end interactions making it easier for myosin to displace Tm. All previously characterized Tms, although able to sterically block the myosin-binding site, are able to bind to actin along with myosin. By showing that Tm can compete directly with myosin for the same binding site these new Tms provide direct evidence for the steric blocking model.

Received for publication, October 16, 2007 , and in revised form, November 13, 2007.

^* This work was supported by Wellcome Trust Grant No. 055881 (to M. A. G.) and by National Institutes of Health grants HL36153 and HL86655 (to W. L.). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

¹ To whom correspondence should be addressed: School of Biological and Chemical Sciences, Queen Mary, University of London, UK. Tel.: 44-207-8827012; Fax: 44-208-9830973; E-mail: r.maytum{at}qmul.ac.uk.

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