Investigation of structure-function interaction of Bombyx mori nuclear polyhedrosis virus polyhedrin with polyhedra protease and RNA. Effect of protease on polyhedrin dissociation during Sepharose 6B gel-filtration

Abstract

It is known that B. mori NPV polyhedra contains protease which cleaves polyhedrin polypeptide chain (m.w. 28500) during dissolution of polyhedra in vitro under alkaline conditions (pH 10.5) to overlapping fragments with mol. weights 25000, 22000, 19000, 10000, and 8000. Besides, polyhedrin is present in solution at pH 10.5 as high mol. weight 13S-(70%) and >13S (30%) associates. Current paper shows that during Sepharose 6B gel-filtration at pH 10.5 of polyhedrin pH 10.5 solution there occurs partial dissociation of high mol. weight associates to unknown earlier 8.5S-associates, 25000 polypeptide and its dimer with sedimentation coefficient 3.4S. Undissociated high mol. weight associates and 8.5S-associates contain the whole polypeptide chain (m.w. 28500) only. During gel-filtration at pH 11.0 of polyhedrin solution with the same pH there occurs complete dissociation of high mol. weight associates to 8.5S-associates, 22000 polypeptide and its dimer with sedimentation coefficient 3.2S. The 8.5S-associate contains the whole 28500 polypeptide chain only. RNA was found in the low mol. weight (and high mol. weight (13S and higher) zones). 8.5S-associates do not contain RNA. After preliminary polyhedra heating at 80-90°C the polyhedra protease does not cleave polyhedrin in pH 10.5 solution and dissociation of high mol. weight associates to 8.5S-associates containing whole polypeptide chain occurs with much lower degree during gel-filtration at pH 10.5. Yet as a result of gel-filtration RNP-complex is released with mol. weight of 20000-25000 and sedimentation 2.9S, containing polypeptide chain with mol. weight of 10000-12000. The effect of the polyhedra protease and RNA on in vivo polyhedrin dissociation and virus realization from polyhedra is discussed.