Perspectives on the Physiology and Structure of Inward-Rectifying K+ Channels in Higher Plants: Biophysical Implications for K+ Uptake

CONTENTS INTRODUCTION 442 PHYSIOLOGICAL FUNCTIONS OF PLANT Ki� CHANNELS . . . . . . . . . . . . 443 Ki� Channels and K+ Uptake . . . ... .. . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . 443 Why Do Plant Cells Take Up K+ via Ki� Channels . . . . . . . . . . . . . . . . . . . . . . 448 BASIC ELECTRICAL PROPERTIES OF PLANT K� CHANNELS . . . . . . . . 449 CLONING AND FUNCTIONAL CHARACTERIZATION OF Ki� CHANNEL cDNAs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 452 Yeast Expression: A Powerful System to Study Transporters. . . . . . . . . . . . . . 452 Structural Features of Ki� Channel Genes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 453 Ki� CHANNEL SELECTIVITY AND BLOCK .... 455 Putative Structural Domains for Ki� Channel Block and Ion Selectivity . . . . 455 Possible Interactions of Na+ with K+ -Uptake and Cation Transporters . . . . 457 Aluminum Toxicity and Block of Ki;; Channels 458 VOLTAGE-DEPENDENT Ki� CHANNEL ACTIVATION . . . ... ... . . ... ... 459 Outward-Rectifying K+ Channels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 461 CYTOSOLIC MODULATION OF K;� CHANNELS 461 PERSPECTIVES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 464