Abstract
Previous studies in our laboratory showed that HeLa cell plasma membranes were recovered from sucrose gradients in two major bands and that the heavier band possessed a putative inhibitor of uncoating of coxsackievirus B3. It has now been found that the mechanism of inhibition is the stabilization of "A" particles against inactivation at 37 degrees C. [3H]uridine-labeled virions converted to A particles by band 4, the heavier band, were four times more stable at 37 degrees C than those produced by band 3. Partially purified A particles from both bands were equally unstable. It was found that the stabilizing factor was extractable by saline from band 4 and remained soluble after centrifugation (109,000 X g for 2 h). Addition to A particles of this soluble factor isolated from either band 4 or band 3 stabilized the A particles. The stabilizing factor could not be replaced by an extract from band 3 or by bovine serum albumin. Thus, the finding that the membrane factor inhibits virus uncoating by stabilizing A particles against spontaneous disruption at 37 degrees C focuses attention on an inherent problem associated with defining receptor-mediated virus uncoating.