The cowpea mosaic virus RNA 1-encoded 112 kDa protein may function as a VPg precursor in vivo

Processing of the 112 kDa (112K) protein encoded by cowpea mosaic virus RNA 1 was examined in cowpea mesophyll protoplasts using a transient expression system. Cleavage of the 112K protein occurred via two alternative pathways either into VPg and 110K (24K + 87K) or into 26K (VPg + 24K) and 87K proteins. The 26K protein can be further cleaved into VPg and 24K proteins. The results support a model in which the 112K protein functions as the precursor of VPg during initiation of replication.

^* Author for correspondence. Fax +31 8370 83584. e-mail Joan. Wellink@MAC.MB.WAU.NL

^† Present address: Department of Virology, Institute of Medical Microbiology, State University, PO Box 320, 2300 AH Leiden, The Netherlands.

^‡ Present address: Laboratoire de Virologie Moleculaire, CNRS, Boulevard Henri IV, 34060 Montpellier cedex, France.