ABSTRACT
Membrane-bound water channels known as aquaporins (AQPs) facilitate water transport across biological membranes along osmotic gradients. Since all living cells depend on their ability to maintain water homeostasis, this must be tightly regulated. In eukaryotes, this is achieved by gating, which involves a conformational change of the
CONTENTS Abstract 53 4.1 Introduction 54 4.2AQP Gating 55
4.2.1Gating of Plant AQPs 56 4.2.1.1PIP Gating Mechanism 56
4.2.2Gating of Yeast AQPs 58 4.2.2.1Gating Mechanism of Aqy1 59
4.2.3Gating of Mammalian AQPs 59 4.2.3.1Gating of AQP0 60 4.2.3.2Are Other Mammalian AQPs Gated? 61
4.3AQP Tra cking 62 4.3.1Tra cking of Mammalian AQPs 62
4.3.1.1Tra cking of AQP2 62 4.3.1.2Tra cking of Other Mammalian AQPs 66
4.3.2Tra cking of Plant AQPs 67 4.4Common Structural emes in Regulated AQPs68
4.4.1AQP Gating Involves a Cytoplasmic Constriction Site 68 4.4.2N-Termini Adopt Two Conformations 68 4.4.3Binding of Ca2+ 70
4.5 Conclusion 70 References 71
protein, thereby physically blocking water transport, or by tra cking in which AQPs are shuttled between intracellular storage sites and the plasma membrane.
