The proteins actin, myosin and titin are big players in the business of muscle contraction. Scientists at the European Molecular Biology Laboratory (EMBL) in Hamburg, Germany, have now examined another muscle protein myomesin which they discovered can stretch up to two-and-a-half times its length, unfolding in a way that was previously unknown. The study is published 14 February in the open-access, online journal PLoS Biology.
Myomesin links muscle filaments, which stretch and contract, so it has to be elastic. Matthias Wilmanns, Head of EMBL Hamburg, and colleagues at the Technical University of Munich in Germany, and The Institute of Cancer Research in the UK, used X-ray crystallography, small-angle X-ray scattering, electron microscopy and atomic force microscopy to reveal the mechanism behind the protein's ability to stretch. The stretchy part of myomesin, analysed by Wilmanns and colleagues, is like a string of pearls, with immunoglobulin (Ig) domains spaced out along an elastic band of structures known as alpha helices.
"Looking at these alpha helices was self-suggestive in itself," says Wilmanns. When the protein is pulled, the helices unfold, whereas the Ig domains do not a finding that could help to solve an ongoing debate in the field about the potential elasticity of Ig domains.
Next, Wilmanns and his group would like to explore myomesin's role in the body and how it interacts and communicates with other muscle components.
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More information: Pinotsis N, Chatziefthimiou SD, Berkemeier F, Beuron F, Mavridis IM, et al. (2012) Superhelical Architecture of the Myosin Filament-Linking Protein Myomesin with Unusual Elastic Properties. PLoS Biol 10(2): e1001261. doi:10.1371/journal.pbio.1001261