Small G Proteins: Arf Family GTPases in Vesicular Transport - Ras Superfamily Small G Proteins: Biology and Mechanisms 2 - page 177

Chapter 9
Small G Proteins: Arf Family GTPases
in Vesicular Transport

Frank Adolf and Felix T. Wieland

Abstract Small GTP-binding proteins of the ADP-ribosylation factor (Arf) family
are key components of trafficking vesicles. In the past three decades a number of
vesicular carriers, whose formation depends on members of the Arf family were
identified, and general molecular mechanisms how these transport carriers form and
operate were established. Here we describe discovery and roles of the
Arf-dependent carriers of the early secretory pathway, the COPI and COPII vesi-
cles. We will discuss their function with regard to molecular mechanisms in coat
recruitment, selection of cargo proteins, vesicle membrane budding/scission, and
vesicle uncoating.

Keywords Biosynthetic membrane transport • Coated transport vesicles • Mem-
brane scission catalyzed by small GTPases

9.1 Introduction

A hallmark of eukaryotic cells is the presence of an elaborate endomembrane
system. Transport of secretory and endocytic cargo between the different organelles
to control and maintain protein and lipid homeostasis is a major task in eukaryotic
cells. The discovery of a secretory pathway and the transport of secretory proteins
along a series of different organelles, in pioneering electron microscopic studies in
exocrine pancreatic cells (Caro and Palade 1964 ; Jamieson and Palade 1967 ), led to
formulation of the vesicle transport hypothesis (Palade 1975 ). According to this
hypothesis transport between the different organelles of the biosynthetic-secretory
and endocytic pathways is achieved by means of directed and regulated vesicular
transport. Today we know that the biogenesis of transport vesicles is driven by