Using X-ray light of DESY’s accelerator DORIS, the team of Matthias Wilmanns from the European Molecular Biology Laboratory EMBL investigated a specific protein that links muscular filaments. This so-called myomesin is able to stretch two-and-a-half times its original length, the scientists report in the professional journal “PLoS Biology” of the Public Library of Science.
“In spite of its enormous importance, we know surprisingly little about muscular elasticity,” Wilmanns points out. Like actin, myosin and titin, myomesin belongs to the elastic muscle proteins. It builds bridges between the main filaments of the muscle, thus stabilizing the muscular structure. With the X-ray light of DESY’s accelerator DORIS and the European synchrotron radiation source ESRF, and with electron and scanning force microscopes, the biologists were able to reveal the structure and functioning of myomesin.
Zoom (17 KB) Myomesin molecules (right) links muscle filaments. Credit: EMBL
The protein looks like a string of beads, with strongly folded immunoglobulin domains, each being connected with an elastic helix (alpha helix). When the protein is expanded, the elastic alpha helices stretch, “a mechanism that to our knowledge has not been observed previously,” the scientists write. In contrast, the immunoglobulin domains – their elasticity is being discussed among biologists – do not seem to unfold. The myomesin analysis is important for all muscles of our body – from the little finger to the heart – and it improves our comprehension of muscle workings.
“Our findings explain how myomesin might adapt its overall length in response to the changing dimensions of the contracting and relaxing muscle, so acting as a highly elastic ribbon that maintains the overall structural organization of the muscle fibers,” the scientists write. “More generally, these findings demonstrate how repetitive domain modules, such as those in myomesin, can provide elasticity to highly organized biological structures.” Next, the team around Wilmanns would like to investigate the role of myomesin in the body and how it is communicating and interacting with other parts of the muscle.
The light sources DORIS, PETRA III and FLASH at Deutsches Elektronen-Synchrotron DESY in Hamburg offer unique research possibilities in many fields, including structural biology. On site, among others, scientists from the European Molecular Biology Laboratory (EMBL), the Center for Free-Electron Laser Science (CFEL) and the University of Hamburg use this light, plus more than 2000 guest scientists per year.
“Superhelical Architecture of the Myosin Filament-Linking Protein Myomesin with Unusual Elastic Properties”; Pinotsis, Chatziefthimiou, et al.; “PLoS Biology” (10(2): e1001261, 2012); DOI: 10.1371/journal.pbio.1001261