The Protein and Nucleic Acid of a Closterovirus Isolated from a Grapevine with Stem-pitting Symptoms

Purified preparations of a closterovirus isolated from a grapevine with stem-pitting symptoms (GSP-AV) had u.v. absorption spectra typical of a nucleoprotein with low nucleic acid content. GSP-AV coat protein had a mol. wt. of about 2.2 × 104. Its nucleic acid was identified as a single-stranded RNA on the basis of (i) base composition (U, 22.3; C, 24.9; A, 24.4; G, 28.4 mol%), (ii) sensitivity to pancreatic ribonuclease A and (iii) melting behaviour (Tm at about 52 °C in 0.15 m-NaCl-0.015 m-sodium citrate). In 2.4% aqueous polyacrylamide gels, GSP-AV RNA had an apparent mol. wt. of 2.55 × 106.