The mechanism of formation of gels from myosin molecules

Abstract

Heat-set myosin gels form the basis of the adhesive that binds particles of meat together in meat products. The manner in which a gel network is formed from myosin has been investigated by studying the aggregates produced when dilute solutions of rabbit skeletal myosin molecules in 0.6 M KC1, 20 mM potassium phosphate, pH 6.5, were heated at a single temperature between 30 and 60°C. The aggregates have been examined by transmission electron microscopy after either negative staining or rotary shadowing.After heating at 30°C for 30 min, no change in structure is detected. After heating at 35°C for 30 min, the two heads of some myosin molecules coalesce and some dimers are formed by aggregation through the heads. After heating at 40°C for 30 min, up to about 13 myosin molecules aggregate through their heads to form a globular mass up to 60 nm across with the tails radiating outwards. At higher temperatures such head-linked oligomers aggregate further. At 48°C oligomers coexist with aggregates formed by the coalescence of two or more oligomers. In such aggregates the globular masses are in close proximity and tails radiate from them. After heating myosin at 50"C, aggregates are formed by the coalescence of more oligomers and the tails are seen only indistinctly. At 60°C the particles formed contain a large number of globular masses and are typically 100 to 200 nm across, occasionally up to 1 pm. It is possible that the globules making up the strands of the gel networks in scanning electron micrographs are composed of similar particles. It is suggested that these globules are formed by head-head interactions but that tail-tail interactions may be important in forming the strands and cross-links of the gel network.When a heat-set myosin gel is compacted by centrifugation, the supernate contains essentially all the LCI and LC3 light chains of the parent molecule but only a small fraction of the LC2 light chains. We suppose that dissociation of the LCl and LC3 chains from the heads creates hydrophobic patches which cause intramolecular and intermolecular head association.

Impact Of Long-Term Storage On The Instrumental Textural Properties Of Frozen Common Carp (Cyprinus Carpio,L.) Flesh

“…[33,34] It is assumed that the freezing temperature of −10 to −20 • C leads to the increase in concentration of dissolved solids by ten times. [35] The most susceptible proteins for denaturation are myofibrillar proteins. It is particularly myosin, as stated in, [36,37] which, during the freezing of cod, reach an 80% deterioration compared to the natural myosin form, whereas under the same conditions, the deterioration of the natural form of actin was negligible.…”

Characterization of protein aggregates following a heating and freezing process

“…However, the heat processes applied on meat generally use higher temperatures and various times, thus potentially producing protein aggregates. A two-step molecular mechanism of protein aggregation has been reported for myosin, with first an association of the heads, possibly through disulphide bridge formation, followed second by oligomer aggregation to form larger clusters, possibly involving association of the tails (Sharp & Offer, 1992;Tazawa, Kato, Katoh, & Konno, 2002). There is little available data on the structure, size variability and shape of these larger aggregates (Brenner et al, 2009).…”

Disruption of secondary structure by oxidative stress alters the cross-linking pattern of myosin by microbial transglutaminase

“…The latter report substantiated an earlier observation that mild oxidation could aid in the gelation of MP . It has long been recognized that individual myosin molecules in non-oxidizing conditions without TGase aggregate into oligomers through head-head (S1) cross-linking via disulfide bonds upon heating from 35°C to 50°C (Sharp & Offer, 1992;Tazawa, Kato, Katoh, & Konno, 2002). With increasing temperatures, these oligomers subsequently connect together through the tail subfragment (rod) to form a gel network.…”