On the Peculiarities of the Aggregation of Multidomain Muscle Proteins

Abstract

Abstract—The hypothesis that formed the basis of this work has been made on our studies that have shown that giant multi-domain muscle proteins of the titin family (titin isoforms and myosin-binding protein C paralogs) form amyloid aggregates in vitro. We have identified a number of features of the amyloid aggregation of the above-mentioned proteins using a number of methods, including X-ray diffraction: (1) the ability to aggregate under reduced ionic strength at pH 7.0; (2) a high aggregation rate; (3) the formation of aggregates that have a quaternary structure like the cross-β structure, which is characteristic of many amyloids; (4) the absence of changes in the secondary structure in the formation of amyloid-like aggregates; and (5) the partial reversibility of amyloid aggregation. In this paper, we raise the following questions. Is amyloid aggregation of these proteins possible in vivo? If so, what could be the functional significance of such aggregation in a muscle cell? We believe that amyloid-like structures can be formed temporarily upon the interaction of individual molecules of multi-domain muscle proteins in the process of muscle contraction in the sarcomere. Such changes would certainly be accompanied an increase in the stiffness of the sarcomeres and the muscle in general, that can play a positive role in preventing harmful effects on the muscle under extreme physical exercise.