Combine first 6 ingredients in a large zip-top plastic bag. Add fish to bag; seal and marinate in refrigerator 1 hour, turning once.
Combine sour cream and next 4 ingredients in a small bowl; set aside.
Remove fish from marinade, reserving marinade. Place fish on grill rack coated with cooking spray; grill 6 minutes on each side or until fish is medium-rare or desired degree of doneness, basting frequently with reserved marinade. Serve with sour cream mixture.