RNA-binding properties and membrane insertion of Melon necrotic spot virus (MNSV) double gene block movement proteins

• Published in: Virology (New York, N.Y.) N.Y.), 2006-12, Vol.356 (1), p.57-67
• Main Authors: Navarro, J.A., Genovés, A., Climent, J., Saurí, A., Martínez-Gil, L., Mingarro, I., Pallás, V.
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; amino acid sequences; Carmovirus; Carmovirus - genetics; Carmovirus - metabolism; Carnation mottle virus; Cucurbitaceae - virology; Gene Deletion; Melon necrotic spot virus; Melon plants; Membrane insertion; membrane proteins; MNSV; Molecular Sequence Data; Movement proteins; Plant Diseases - virology; Plant Viral Movement Proteins - chemistry; Plant Viral Movement Proteins - genetics; Plant Viral Movement Proteins - metabolism; plant viruses; RNA-binding domain; RNA-binding proteins; RNA-Binding Proteins - chemistry; RNA-Binding Proteins - genetics; RNA-Binding Proteins - metabolism; Sequence Alignment; viral movement proteins; viral proteins
• ISSN: 0042-6822; 1096-0341
• DOI: 10.1016/j.virol.2006.07.040

Advances in structural and biochemical properties of carmovirus movement proteins (MPs) have only been obtained in p7 and p9 from Carnation mottle virus (CarMV) . Alignment of carmovirus MPs revealed a low conservation of amino acid identity but interestingly, similarity was elevated in regions associated with the functional secondary structure elements reported for CarMV which were conserved in all studied proteins. Nevertheless, some differential features in relation with CarMV MPs were identified in those from Melon necrotic virus (MNSV) (p7A and p7B). p7A was a soluble non-sequence specific RNA-binding protein, but unlike CarMV p7, its central region alone could not account for the RNA-binding properties of the entire protein. In fact, a 22-amino acid synthetic peptide whose sequence corresponds to this central region rendered an apparent dissociation constant ( K d) significantly higher than that of the corresponding entire protein (9 mM vs. 0.83–25.7 μM). This p7A-derived peptide could be induced to fold into an alpha-helical structure as demonstrated for other carmovirus p7-like proteins. Additionally, in vitro fractionation of p7B transcription/translation mixtures in the presence of ER-derived microsomal membranes strongly suggested that p7B is an integral membrane protein. Both characteristics of these two small MPs forming the double gene block (DGB) of MNSV are discussed in the context of the intra- and intercellular movement of carmovirus.