SB401, a pollen-specific protein from Solanum berthaultii, binds to and bundles microtubules and F-actin
We characterize a novel, pollen-specific, microtubule-associated protein, SB401, found in Solanum berthaultii. This protein binds to and bundles taxol-stabilized microtubules and enhances tubulin polymerization in a concentration-dependent manner, particularly at lower temperatures. Electron microscopy revealed that the protein decorates the entire length of microtubules. Cross-linking and electrophoresis studies showed that SB401 protein forms dimers, and suggest that dimerization could account for bundling. Double immunofluorescent staining of pollen tubes of S. berthaultii showed that SB401 protein co-localized with cortical microtubule bundles. SB401 protein also binds to and bundles actin filaments, and could connect actin filaments to microtubules. SB401 protein had a much higher affinity for microtubules than for actin filaments. In the presence of both cytoskeletal elements, the protein preferentially bound microtubules to form bundles. These results demonstrate that SB401 protein may have important roles in organizing the cytoskeleton in pollen tubes.
Document Type: Research Article
Affiliations: 1: State Key Laboratory of Plant Physiology and Biochemistry, Department of Plant Sciences, College of Biological Sciences, China Agricultural University, Beijing 100094 2: State Key Laboratory of AgroBiotechnology, Department of Biochemistry and Molecular Biology, College of Biological Sciences, China Agricultural University, Beijing 100094, China
Publication date: August 1, 2007