title: Cotton GhKCH2, a plant-specific kinesin, is low-affinitive and nucleotide-independent as binding to microtubule.
abstract: Kinesin is an ATP-driven microtubule motor protein that plays important roles in control of microtubule dynamics, intracellular transport, cell division and signal transduction. The kinesin superfamily is composed of numerous members that are classified into 14 subfamilies. Animal kinesins have been well characterized. In contrast, plant kinesins have not yet to be characterized adequately. Here, a novel plant-specific kinesin gene, GhKCH2, has been cloned from cotton (Gossypium hirsutum) fibers and biochemically identified by prokaryotic expression, affinity purification, ATPase activity assay and microtubule-binding analysis. The putative motor domain of GhKCH2, M396-734 corresponding to amino acids Q396-N734 was fused with 6xHis-tag, soluble-expressed in E. coli and affinity-purified in a large amount. The biochemical analysis demonstrated that the basal ATPase activity of M396-734 is not activated by Ca2+, but stimulated 30-fold max by microtubules. The enzymatic activation is microtubule-concentration-dependent, and the concentration of microtubules that corresponds to half-maximum activation was about 11 microM, much higher than that of other kinesins reported. The cosedimentation assay indicated that M396-734 could bind to microtubules in vitro whenever the nucleotide AMP-PNP is present or absent. As a plant-specific microtubule-dependent kinesin with a lower microtubule-affinity and a nucleotide-independent microtubule-binding ability, cotton GhKCH2 might be involved in the function of microtubules during the deposition of cellulose microfibrils in fibers or the formation of cell wall.
authors.affiliation: State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing 100094, China.
authors.forename: Tao
authors.initials: T
authors.lastname: Xu
authors.forename: Xuewei
authors.initials: X
authors.lastname: Sun
authors.forename: Shiling
authors.initials: S
authors.lastname: Jiang
authors.forename: Dongtao
authors.initials: D
authors.lastname: Ren
authors.forename: Guoqin
authors.initials: G
authors.lastname: Liu
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism; D000595:Amino Acid Sequence; D001665:Binding Sites; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000737:chemistry / Q000235:genetics; D003368:Gossypium / Q000235:genetics / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D016547:Kinesins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008870:Microtubules / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009711:Nucleotides / Q000378:metabolism*; D010802:Phylogeny; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid
chemical_list: D018076:DNA, Complementary; D009711:Nucleotides; D010940:Plant Proteins; D000251:Adenosine Triphosphatases; D016547:Kinesins