Disease relevance of MP

• The internal ribosome entry sites (IRES), IRES(CP,148)(CR) and IRES(MP,75)(CR), precede the coat protein (CP) and movement protein (MP) genes of crucifer-infecting tobamovirus (crTMV), respectively [1].
• Both these mutants were also rescued by the tobacco mosaic virus (TMV) movement protein (MP) [2].
• Cucumber mosaic virus (CMV, a cucumovirus) and Brome mosaic virus (BMV, a bromovirus) require the coat protein (CP) in addition to the 3a movement protein (MP) for cell-to-cell movement, while Cowpea chlorotic mottle virus (CCMV, a bromovirus) does not [3].
• The replacement of the CP gene in RNA 3 by a mutant gene encoding a CP defective in virion formation did not affect cell-to-cell transport of the chimera's with a functional MP [4].
• A GST pull-down technique was used to demonstrate for the first time that the C-terminal 44 amino acids of the MP of a virus belonging to the family Bromoviridae interact specifically with AMV virus particles [4].

High impact information on MP

• Microtubules may target the MP to plasmodesmata, the intercellular channels that connect adjacent cells [5].
• A novel method for delivering non-plasmalemma-permeable fluorescent probes to the cytosol of spongy mesophyll cells of tobacco leaves was used to study plasmodesmatal size exclusion limits in transgenic plants that express the MP gene [6].
• Furthermore, TMV encoding the MP mutant mimicking phosphorylation was unable to spread from cell to cell in inoculated tobacco plants [7].
• To understand this process better, a cell wall-associated protein that specifically binds the viral MP was purified from tobacco leaf cell walls and identified as pectin methylesterase (PME) [8].
• Disruption of the microtubule cytoskeleton in situ with pharmacological agents, or by silencing of the alpha-tubulin gene, had no significant effect on the spread of TMV vectors expressing wild-type MP (MP(WT)) and did not prevent the accumulation of MP(WT) in plasmodesmata [9].

Biological context of MP

• Computer analysis predicted two stem-loop structures (SL1 and SL2) upstream of the MP sgRNA transcription start site [10].
• The MP of CymMV consists of three overlapping open reading frames, together called the triple-gene block (TGB) [11].
• The cell-to-cell movement of a movement-deficient CymMV was restored in transgenic plants carrying the ORSV MP transgene [11].
• The conserved amino acid sequences in the MP can be used for the classification of tobamoviruses [12].
• In the present work, we have found that the 228-nt region upstream of the movement protein (MP) gene of crTMV RNA (IRES(MP,228)(CR)) contained an IRES element that directed in vitro translation of the 3'-proximal reporter genes from chimeric dicistronic transcripts [13].

Anatomical context of MP

• The distribution of the MP is disrupted by treatments that disrupt microtubules, but not by cytochalasin B, which disrupts filamentous F-actin [5].
• To explore the structural properties of MP, the full-length recombinant MP gene was expressed in Escherichia coli, and one-step purification from solubilized inclusion bodies was accomplished by using anion exchange chromatography [14].
• We developed a model of VRCs that shows a clear association of MP with and surrounding the endoplasmic reticulum [15].
• Microsomes isolated from infected leaves contain MP [16].
• Significant levels of the MP were detected in a crude membrane/organelle fraction and a soluble fraction in younger leaves but decreased to low levels in older leaves [17].

Associations of MP with chemical compounds

• Soluble MP was maintained at >4 mg/ml without aggregation and displayed approximately 70% alpha-helical conformation in the presence of urea and SDS [14].
• CMV RNA fluorescently labeled with the nucleotide-specific TOTO-1 iodide dye, when coinjected with unlabeled CMV 3a movement protein (MP), moved rapidly into the surrounding mesophyll cells in mature tobacco leaves of vector control and untransformed plants [18].
• A mutant virus designated 37A238A was constructed; this virus lacked two serine residues within the MP, which prevented its phosphorylation [19].
• MP which contained threonine at position 37 was phosphorylated, but the stability of the MP in vivo was very low [20].
• MP mutants in which serine was replaced by alanine at positions 37 and 238 (LQ37A238A) or at position 37 only (LQ37A) were not phosphorylated, and mutant viruses did not infect tobacco or tomato plants [20].

Analytical, diagnostic and therapeutic context of MP

• Deletion analysis and site-directed mutagenesis suggested that SL1 secondary structure, but not its sequence, was required for MP sgRNA promoter activity, whereas a 39-nt deletion removing most of the SL2 region increased MP sgRNA accumulation fourfold [10].
• A microinjection procedure was used to investigate the effects of the modified TMV MP on plasmodesmatal size-exclusion limits [21].
• We used anion-exchange chromatography and preparative sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) to obtain highly purified 30-kDa MP, which migrated as a single band in native PAGE [22].
• This was evidenced by the size of the MP produced and by sequence analysis of reverse-transcribed PCR-amplified products, following infection by the modified virus [23].
• To expand our understanding of the MP function, we analyzed events occurring during the intracellular and intercellular targeting of MPTMV and MPNT-1 when expressed as a fusion protein to green fluorescent protein (GFP), either by biolistic bombardment in a viral-free system or from a recombinant virus [24].

References