X -ray studies of the molecular structure of myosin

Abstract

[P lates [15][16][17] The X -ra y an d elastic properties of m yosin are found to resem ble m ost closely, n o t those of n a tu ra l k eratin , b u t those of k e ra tin th a t has suffered breakdow n am ong th e cross-linkages (including disulphide bridges) of th e polypeptide grid. The su p erco n tractio n of m yosin cannot be explained as due sim ply to d isorientation of long th in u n its : it m u st involve a fu rth er folding of th e polypeptide chain system . The fact th a t m yosin an d k eratin are sim ilar in b o th m olecular configuration an d elastic properties is discussed in th e light of recent X -ra y an d chem ical findings, and th e X -ray in terp retatio n is given of th e d e n a tu ra tio n of m yosin. I n t r o d u c t o r yX-ray studies of the molecular structure and properties of animal hairs (Astbury and Street 1931; Astbury and Woods 1933; Astbury and Sisson 1935 ' Woods 1938)* lead naturally to comparable studies of muscle tissue, if only because both types of structure are protein and fibrous, but par ticularly because both show similar long-range elastic phenomena and give similar X-ray photographs (Astbury 1933a(Astbury , 1934. Previous X-ray studies of muscle (Herzog and Jancke

How molecular motors extract order from chaos (a key issues review)

“…Early work on muscles was inspired by experience with humanbuilt machinery. Before the sliding filament hypoth esis, muscle was believed to work by the coiling of springlike proteins [17]. The tilting crossbridge idea of Hugh Huxley was also quite mechanical and, while physiologically correct, did not clearly explain how energy was transduced from chemical to mechanical form.…”

Invertebrate muscles: Thin and thick filament structure; molecular basis of contraction and its regulation, catch and asynchronous muscle

“…Early work showed that the sliding filament hypothesis (which was proposed on the basis of work in striated muscle) applied to molluscan smooth muscles as well (Dörr and Portzehl, 1954;Hanson and Lowy, 1959;Razumova et al, 1970;Millman and Elliott, 1972;Sugi and Tsuchiya, 1975). Molluscan muscle was also a preparation used in the extremely early X-ray diffraction studies of helical proteins (Astbury and Dickinson, 1940;Astbury, 1946;Fraser et al, 1965). X-ray reflections arising from the thin and thick filaments in these muscles are very well separated .…”