Plant potyvirus RNAs have a virus protein covalently attached at their 5′-end: the VPg (virus protein genome-linked). In part because of its position at the 5′end of the virus RNA, the VPg has been speculated to play a role in virus translation and replication. We report that the VPg of Turnip mosaic virus (TuMV) interacts with, and does not disrupt, the translation initiation complex eIF(iso)4E-eIF(iso)4G. The purification of VPgPro or 6K2VPgPro by affinity chromatography from infected plant tissue also led to the recovery of eIF(iso)4G. The cap analogue m 7 GTP competed with the binding of VPg to both eIF(iso)4E and the eIF(iso)4E-eIF(iso)4G complex. This suggested that the viral VPg bound to the translation initiation complex but that interaction did not result in disassociation of the subunits but rather in competition for the binding of the 5′ cap structure. This would result in decreased affinity of the translation initiation machinery for capped cellular mRNAs.