What molecule am I?
Titin1, also called connectin, is the largest known protein. It is found in the striated muscle tissue of humans and other vertebrates; homologous proteins exist in invertebrate animal families. Human titin is >1 µm long and consists of 244 folded protein domains. Adults’ bodies contain ≈500 g of titin.
In 1954, Reiji Natori at the Jikei University School of Medicine (Tokyo) proposed an elastic structure in muscle to explain how muscles stretch and contract. The first comprehensive description of titin was reported in 1979 by Kuan Wang*, Janela McClure, and Ann Tu at the University of Texas at Austin. They used electrophoresis to purify “a combination of two uncommonly large proteins, designated as titin, from chicken breast myofibrils”. They concluded that titin is “a structurally conserved myofibrillar component of vertebrate and invertebrate striated muscles”.
Since the publication of Wang et al.’s pioneering work, a large body of research on titin has appeared. In 2019, Michael Gotthardt at the Max Delbrück Center for Molecular Medicine, the Charité University of Medicine, and the German Center for Cardiovascular Research (all in Berlin) and 11 collaborators in Germany, the United States, and Japan reported details of titin’s lifecycle: how it is biosynthesized and integrated into the sacromere (the smallest functional unit of striated muscle tissue), and how it eventually detaches and degrades. The authors stated that there is still much to learn about titin synthesis and assembly.
A ScienceDirect compilation provides examples of additional research on titin.
1. From “titan protein”. Not to be confused with tutin, the Molecule of the Week for May 2, 2022.
Learn more about this molecule from CAS, the most authoritative and comprehensive source for chemical information.