**Acknowledgements**

The authors are grateful to Drs. L.A. Tskhovrebova and J.Trinick for kindly providing the antibodies against titin. The authors also thank Sergey Udaltsov for helpful discussions on electrophoretic techniques. This work was financially supported by the Russian Foundation for Basic Research (project No. 17-04-00326) and by the Russian Science Foundation (project No. 18-15-00062).

† In memoriam to Dr. Zoya Podlubnaya.
