Correlated changes in mechanical properties of the intersegmental membrane and bonding between proteins in the female adult locust

Abstract

When the female locust ecdyses into the adult instar the intersegmental membranes which will extend when the female digs the oviposition hole are stiff and inextensible. Extensibility of the membranes develops later, and is under the control of the corpus allatum: allatectomy prevents the development of extensibility. The difference in extensibility and stiffness of the membranes before and after sexual maturation can be accounted for as a change in the bonding in the protein matrix of the cuticle. Electrophoretic analysis of the cuticular proteins dissociated by SDS shows that there are five major proteins in the cuticle, and that these do not change when the membrane becomes extensible. The differing responses of the two states of the cuticle to sequential extraction in water, 0·5 M KCl, 7 M urea, and 1·0 M NaOH at 60°C suggest that the change is one of reduction in hydrogen bonding. Simple calculations on mechanical data suggest that in the unstretchable state there is one interchain bond every 370 or so amino acid residues. This may allow sufficiently specific site definition for an enzyme to be involved in the breakdown of hydrogen bonding. An E.M. of a possible enzyme package in the cuticle is presented.