Rab geranylgeranylation occurs preferentially via the pre-formed REP-RGGT complex and is regulated by geranylgeranyl pyrophosphate
Rab geranylgeranylation occurs preferentially via the pre-formed REP-RGGT complex and is regulated by geranylgeranyl pyrophosphate
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DOI：
10.1042/bj20080662
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发表时间：
2008-10-01
影响因子：
4.1
通讯作者：
Seabra, Miguel C.
中科院分区：
文献类型：
--
作者：
Baron, Rudi A.;Seabra, Miguel C.
Rab gtpase的戊烯酰化（或香叶酰化）是由RGGT （Rab geranylgeranyl transferase）催化的，需要REP （Rab escort protein）。在经典途径中，REP首先与未烯丙基化的Rab结合，然后被RGGT烯丙基化。然后这个复合物结合Rab蛋白并使之戊酰化。在本文中，我们发现RGGT结合缺陷的REP突变体（REP1 F282L和REP1 F282L/V290F）在体外戊酰化反应中无法与野生型REP竞争。当在细胞中过度表达时，REP野生型和突变体无法与内源性未戊酰化的Rains形成稳定的胞质复合物。这些结果表明，另一种途径可能在体内占主导地位。我们还扩展了先前的建议，即GGPP（香叶基焦磷酸香叶基）是戊酰化反应的所有变构调节剂。我们观察到REP-RGGT复合物在体内形成，在缺乏细胞内GGPP的情况下是不稳定的。RGGT通过稳定可溶性REP-RGGT-Rab- gg（香叶基-香叶基化Rab）复合物，提高体外REP从膜中提取内源性烯丙基化Rab的能力。这种作用是由GGPP调节的，GGPP促进RGGT和rep - rabb - gg的解离，从而允许将烯酰化的Rabs传递到膜上。
Prenylation (or geranylgeranylation) of Rab GTPases is catalysed by RGGT (Rab geranylgeranyl transferase) and requires REP (Rab escort protein). In the classical pathway, REP associates first with unprenylated Rab, which is then prenylated by RGGT In the alternative pathway, REP associates first with RGGT; this complex then binds and prenylates Rab proteins. In the present paper we show that REP mutants defective in RGGT binding (REP1 F282L and REP1 F282L/V290F) are unable to compete with wild-type REP in the prenylation reaction in vitro. When over-expressed in cells, REP wild-type and mutants are unable to form stable cytosolic complexes with endogenous unprenylated Rains. These results suggest that the alternative pathway may predominate in vivo. We also extend previous suggestions that GGPP (geranylgeranyl pyrophosphate) acts as ail allosteric regulator of the prenylation reaction. We observed that REP-RGGT complexes are formed in vivo and are unstable in the absence of intracellular GGPP. RGGT increases the ability of REP to extract endogenous prenylated Rabs from membranes in vitro by stabilizing a Soluble REP-RGGT-Rab-GG (geranyl-geranylated Rab) complex. This effect is regulated by GGPP, which promotes the dissociation of RGGT and REP-Rab-GG to allow delivery of prenylated Rabs to membranes.