Hoyle Henry D, Turner F Rudolf, Raff Elizabeth C
Department of Biology, Indiana University, Bloomington, Indiana 47405, USA.
Cell Motil Cytoskeleton. 2008 Apr;65(4):295-313. doi: 10.1002/cm.20261.
Drosophila melanogaster sperm tubulins are posttranslationally glutamylated and glycylated. We show here that axonemes are the substrate for these tubulin C-terminal modifications. Axoneme architecture is required, but full length, motile axonemes are not necessary. Tubulin glutamylation occurs during or shortly after assembly into the axoneme; only glutamylated tubulins are glycylated. Tubulins in other testis microtubules are not modified. Only a small subset of total Drosophila sperm axoneme tubulins have these modifications. Biochemical fractionation of Drosophila sperm showed that central pair and accessory microtubules have the majority of poly-modified tubulins, whereas doublet microtubules have only small amounts of mono- and oligo-modified tubulins. Glutamylation patterns for different beta-tubulins experimentally assembled into axonemes were consistent with utilization of modification sites corresponding to those identified in other organisms, but surrounding sequence context was also important. We compared tubulin modifications in the 9 + 9 + 2 insect sperm tail axonemes of Drosophila with the canonical 9 + 2 axonemes of sperm of the sea urchin Lytichinus pictus and the 9 + 0 motile sperm axonemes of the eel Anguilla japonica. In contrast to Drosophila sperm, L. pictus sperm have equivalent levels of modified tubulins in both doublet and central pair microtubule fractions, whereas the doublets of A. japonica sperm exhibit little glutamylation but extensive glycylation. Tubulin C-terminal modifications are a prevalent feature of motile axonemes, but there is no conserved pattern for placement or amount of these
黑腹果蝇精子微管蛋白在翻译后会发生谷氨酰胺化和糖基化修饰。我们在此表明轴丝是这些微管蛋白C末端修饰的底物。轴丝结构是必需的，但全长、有运动能力的轴丝并非必要条件。微管蛋白谷氨酰胺化在组装到轴丝过程中或之后不久发生；只有谷氨酰胺化的微管蛋白会进行糖基化修饰。睾丸中其他微管中的微管蛋白未被修饰。果蝇精子轴丝微管蛋白中只有一小部分具有这些修饰。果蝇精子的生化分级分离表明，中央微管对和辅助微管含有大部分多修饰的微管蛋白，而双联微管仅含有少量单修饰和寡修饰的微管蛋白。通过实验组装到轴丝中的不同β-微管蛋白的谷氨酰胺化模式与在其他生物体中鉴定出的修饰位点的利用情况一致，但周围的序列背景也很重要。我们比较了果蝇9 + 9 + 2昆虫精子尾部轴丝与海胆光棘球海胆精子的典型9 + 2轴丝以及日本鳗鲡9 + 0运动精子轴丝中的微管蛋白修饰情况。与果蝇精子不同，光棘球海胆精子在双联微管和中央微管对部分中修饰微管蛋白的水平相当，而日本鳗鲡精子的双联微管几乎没有谷氨酰胺化，但糖基化程度很高。微管蛋白C末端修饰是运动轴丝的一个普遍特征，但这些修饰的位置或数量并没有保守的模式。
