Ultra short yeast tropomyosins show novel Myosin regulation

Maytum, Robin and Hatch, Victoria and Konrad, Manfred and Lehman, William and Geeves, Michael A. (2008) Ultra short yeast tropomyosins show novel Myosin regulation. Journal of Biological Chemistry, 283 (4). pp. 1902-1910. ISSN 0021-9258. (The full text of this publication is not available from this repository)

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Official URL
http://dx.doi.org/10.1074/jbc.M708593200

Abstract

Tropomyosin (Tm) is an alpha-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%) approximately 0.5 mum). 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.

Item Type: Article
Additional information: Journal Article United States
Subjects: Q Science
Divisions: Faculties > Science Technology and Medical Studies > School of Biosciences > Protein Science Group
Depositing User: Michael Geeves
Date Deposited: 15 May 2009 10:17
Last Modified: 20 May 2014 15:45
Resource URI: http://kar.kent.ac.uk/id/eprint/13221 (The current URI for this page, for reference purposes)
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