2010م - 1444هـ
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Abstract

Although the genes that encode membrane proteins make about 30% of the sequenced genomes,

the evolution of membrane proteins and their origins are still poorly understood.

Here we address this topic by taking a closer look at those membrane proteins the ancestors

of which were present in the Last Universal Common Ancestor, and in particular, the

F/V-type rotating ATPases. Reconstruction of their evolutionary history provides hints

for understanding not only the origin of membrane proteins, but also of membranes themselves.

We argue that the evolution of biological membranes could occur as a process of coevolution

of lipid bilayers and membrane proteins, where the increase in the ion-tightness

of the membrane bilayer may have been accompanied by a transition from amphiphilic,

pore-forming membrane proteins to highly hydrophobic integral membrane complexes.

1 Introduction

Th e origins of membrane proteins are inextricably coupled with the origin of lipid

membranes. Indeed, membrane proteins, which contain hydrophobic stretches and

are generally insoluble in water, could not have evolved in the absence of functional

membranes, while purely lipid membranes would be impenetrable and hence useless

without membrane proteins. Th e origins of biological membranes – as complex

cellular devices that control the energetics of the cell and its interactions with the

surrounding world (Gennis 1989) – remain obscure (Deamer 1997; Pereto et al.

2004)