Dysfunctionality of a tobacco mosaic virus movement protein mutant mimicking threonine 104 phosphorylation.

• Replication of tobacco mosaic virus (TMV) is connected with endoplasmic reticulum (ER)-associated membranes at early stages of infection. This study reports that TMV movement protein (MP)-specific protein kinases (PKs) associated with the ER of tobacco were capable of phosphorylating Thr(104) in TMV MP. The MP-specific PKs with apparent molecular masses of about 45-50 kDa and 38 kDa were revealed by gel PK assays. Two types of mutations were introduced in TMV MP gene of wild-type TMV U1 genome to substitute Thr(104) by neutral Ala or by negatively charged Asp. Mutation of Thr(104) to Ala did not affect the size of necrotic lesions induced by the mutant virus in Nicotiana tabacum Xanthi nc. plants. Conversely, mutation of Thr to Asp mimicking Thr(104) phosphorylation strongly inhibited cell-to-cell movement. The possible role of Thr(104) phosphorylation in TMV MP function is discussed.

Nyckelord

Amino Acid Substitution

Biological Transport

Endoplasmic Reticulum/enzymology

Molecular Weight

Mutation

Phosphorylation

Plant Viral Movement Proteins

Protein Kinases/chemistry/metabolism

Threonine/*metabolism

Tobacco/virology

Tobacco Mosaic Virus/*metabolism

Viral Proteins/*metabolism

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