Tropomyosin diffraction pattern

Parry, D. A. D., and Squire, J. M. (1973). The structural role of tropomyosin in muscle regulation Analysis of the X-ray diffraction patterns from relaxed and contracting muscles. /. Mol. Biol. 37, 33—55. 

The diffraction pattern from troponin is very different. Here, there is one troponin complex for each tropomyosin molecule, but the end-to-end repeat along the tropomyosin strands is about 385 A It is longer than the actin filament crossover repeat of just over 357 A in vertebrate muscles (Fig. 11A and B). Because much of the troponin complex is globular, unlike tropomyosin, it shows very marked discontinuous density every 385 A along each strand of the actin filament, with the troponins in opposite strands axially shifted by the actin monomer subunit translation h of... 

After the war, Bailey returned to studies on muscle, and announced in 1946 the isolation from vertebrate muscle of tropomyosin B, a new myofibrillar protein with unusual properties. This achievement and the later discovery of the family of tropomyosins A are Bailey s most important contributions to the muscle field. The latter protein was shown to be responsible for the paramyosin X-ray diffraction pattern characteristic of molluscan adductor muscles and opened up a new field of interest. The tropomyosins possess a number of remarkable properties which are just those which we would have expected to excite his interest—one cannot help feeling that these proteins were almost custom-built for him. Their function is still something of a mystery but the... 

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