Allen-Baume Victoria, Ségui Bruno, Cockcroft Shamshad
Department of Physiology, University College London, WC1E 6JJ, London, UK.
FEBS Lett. 2002 Oct 30;531(1):74-80. doi: 10.1016/s0014-5793(02)03412-9.
Monomeric transport of lipids is carried out by a class of proteins that can shield a lipid from the aqueous environment by binding the lipid in a hydrophobic cavity. One such group of proteins is the phosphatidylinositol transfer proteins (PITP) that can bind phosphatidylinositol and phosphatidylcholine and transfer them from one membrane compartment to another. PITPs are found in both unicellular and multicellular organisms but not bacteria. In mice and humans, the PITP domain responsible for lipid transfer is found in five proteins, which can be classified into two classes based on sequence. Class I PITPs comprises two family members, alpha and beta, small 35 kDa proteins with a single PITP domain which are ubiquitously expressed. Class IIA PITPs (RdgBalphaI and II) are larger proteins possessing additional domains that target the protein to membranes and are only able to bind lipids but not mediate transfer. Finally, Class IIB PITP (RdgBbeta) is similar to Class I in size (38 kDa) and is also ubiquitously expressed. Class III PITPs, exemplified by the Sec14p family, are found in yeast and plants but are unrelated in sequence and structure to Class I and Class II PITPs. In this review we discuss whether PITP proteins are passive transporters or are regulated proteins that are able to couple their transport and binding properties to specific biological functions including inositol lipid signalling and membrane turnover.
脂质的单体运输由一类蛋白质完成，这类蛋白质可通过将脂质结合在疏水腔中来使其免受水环境的影响。其中一组这样的蛋白质是磷脂酰肌醇转移蛋白（PITP），它能结合磷脂酰肌醇和磷脂酰胆碱，并将它们从一个膜区室转移到另一个膜区室。PITP存在于单细胞和多细胞生物中，但不存在于细菌中。在小鼠和人类中，负责脂质转移的PITP结构域存在于五种蛋白质中，根据序列可将它们分为两类。I类PITP包括两个家族成员，α和β，是35 kDa的小蛋白质，具有单个PITP结构域，广泛表达。IIA类PITP（RdgBalphaI和II）是较大的蛋白质，具有将蛋白质靶向膜的额外结构域，只能结合脂质但不能介导转移。最后，IIB类PITP（RdgBbeta）在大小上与I类相似（38 kDa），也广泛表达。III类PITP以Sec14p家族为代表，存在于酵母和植物中，但在序列和结构上与I类和II类PITP无关。在本综述中，我们讨论了PITP蛋白是被动转运蛋白还是受调控的蛋白，它们是否能够将其转运和结合特性与特定的生物学功能（包括肌醇脂质信号传导和膜更新）联系起来。
