Phillips S E, Sha B, Topalof L, Xie Z, Alb J G, Klenchin V A, Swigart P, Cockcroft S, Martin T F, Luo M, Bankaitis V A
Department of Cell Biology, University of Alabama at Birmingham 35294-0005, USA.
Mol Cell. 1999 Aug;4(2):187-97. doi: 10.1016/s1097-2765(00)80366-4.
Yeast phosphatidylinositol transfer protein (Sec14p) is essential for Golgi secretory function. It is widely accepted, though unproven, that phosphatidylinositol transfer between membranes represents the physiological activity of phosphatidylinositol transfer proteins (PITPs). We report that Sec14pK66,239A is inactivated for phosphatidylinositol, but not phosphatidylcholine (PC), transfer activity. As expected, Sec14pK66,239A fails to meet established criteria for a PITP in vitro and fails to stimulate phosphoinositide production in vivo. However, its expression efficiently rescues the lethality and Golgi secretory defects associated with sec14-1ts and sec14 null mutations. This complementation requires neither phospholipase D activation nor the involvement of a novel class of minor yeast PITPs. These findings indicate that PI binding/transfer is remarkably dispensable for Sec14p function in vivo.
酵母磷脂酰肌醇转移蛋白（Sec14p）对于高尔基体分泌功能至关重要。尽管未经证实，但膜间磷脂酰肌醇转移代表磷脂酰肌醇转移蛋白（PITPs）的生理活性这一观点已被广泛接受。我们报告称，Sec14pK66,239A对磷脂酰肌醇的转移活性失活，但对磷脂酰胆碱（PC）的转移活性未失活。正如预期的那样，Sec14pK66,239A在体外不符合PITP的既定标准，并且在体内无法刺激磷酸肌醇的产生。然而，其表达有效地挽救了与sec14-1ts和sec14基因缺失突变相关的致死性和高尔基体分泌缺陷。这种互补作用既不需要磷脂酶D的激活，也不需要一类新型的次要酵母PITPs的参与。这些发现表明，PI结合/转移对于Sec14p在体内的功能而言明显是不必要的。
