Replication of the flavivirus Kunjin: proteins, glycoproteins, and maturation associated with cell membranes.

Kunjin virus-infected Vero cells were disrupted and the membranes separated by equilibrium centrifugation in discontinuous sucrose density gradients. Relatively pure fractions of smooth, rough and plasma membranes were obtained. Radioisotopic labeling experiments showed that virus-specific RNA and protein syntheses occur predominantly on smooth and rough membranes, respectively. Electrophoretic profiles of viral proteins were similar in all membrane fractions. Glucosamine, mannose, galactose and fucose were incorporated into viral glycoproteins in decreasing proportions. In smooth membranes only, the envelope glycoprotein was deficient in glucosamine but not in mannose. Rapid transfer of newly synthesized proteins to plasma membranes occurred; some enrichment therein of the largest nonstructural protein was detected. In electron micrographs, mature virions were observed only in fractions containing rough membranes. In thin sections of whole cells at 24 hr postinfection, most mature virions were in vesicles, but in some cells virions and possibly precursor particles were in lamella-like arrays within cisternae bounded by modified membranes.