Kozubowski Lukasz, Larson Jennifer R, Tatchell Kelly
Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, Shreveport, LA 71130, USA.
Mol Biol Cell. 2005 Aug;16(8):3455-66. doi: 10.1091/mbc.e04-09-0764. Epub 2005 May 18.
In the yeast Saccharomyces cerevisiae, septins form a scaffold in the shape of a ring at the future budding site that rearranges into a collar at the mother-bud neck. Many proteins bind asymmetrically to the septin collar. We found that the protein Bni4-CFP was located on the exterior of the septin ring before budding and on the mother side of the collar after budding, whereas the protein kinase Kcc4-YFP was located on the interior of the septin ring before budding and moved into the bud during the formation of the septin collar. Unbudded cells treated with the actin inhibitor latrunculin-A assembled cortical caps of septins on which Bni4-CFP and Kcc4-YFP colocalized. Bni4-CFP and Kcc4-YFP also colocalized on cortical caps of septins found in strains deleted for the genes encoding the GTPase activating proteins of Cdc42 (RGA1, RGA2, and BEM3). However, Bni4-CFP and Kcc4-YFP were still partially separated in mutants (gin4, elm1, cla4, and cdc3-1) in which septin morphology was severely disrupted in other ways. These observations provide clues to the mechanisms for the asymmetric localization of septin-associated proteins.
在酿酒酵母中，隔膜蛋白在未来的出芽位点形成一个环状支架，该支架会重排为母细胞 - 芽颈处的领圈状结构。许多蛋白质不对称地结合到隔膜蛋白领圈上。我们发现，蛋白质Bni4 - CFP在出芽前位于隔膜蛋白环的外部，出芽后位于领圈的母细胞一侧，而蛋白激酶Kcc4 - YFP在出芽前位于隔膜蛋白环的内部，并在隔膜蛋白领圈形成过程中移入芽中。用肌动蛋白抑制剂拉特罗菌素 - A处理的未出芽细胞组装了隔膜蛋白的皮质帽，Bni4 - CFP和Kcc4 - YFP在其上共定位。在缺失编码Cdc42的GTPase激活蛋白（RGA1、RGA2和BEM3）的基因的菌株中发现的隔膜蛋白皮质帽上，Bni4 - CFP和Kcc4 - YFP也共定位。然而，在隔膜蛋白形态以其他方式严重破坏的突变体（gin4、elm1、cla4和cdc3 - 1）中，Bni4 - CFP和Kcc4 - YFP仍部分分离。这些观察结果为隔膜蛋白相关蛋白不对称定位的机制提供了线索。
