Leghemoglobin and Rhizobium Respiration

Abstract

INTRODUCTION 444 LEGHEMOGLOBIN 445 Occurrence, Purification, Sequence Analysis 445 Biosynthesis and its Control; Genetic Origin 446 Maintenance, Turnover, and Degradation 448 Leghemoglobin Structure in Relation to Oxygen Reactivity 449 lntracellular Location of Leghemoglobin 451 LEGUME BACTEROIDS AND THE OXYGEN PARADOX 452 Nitrogenase Location and Oxygen Lability: Possible Protective Mechanisms ......... 452 Cytochrome Variation Among Free-living Rhizobia and Bacteroids 453 Periplasmic Location of Bacteroid Oxidases? 455 LEGHEMOGLOBIN A D RHIZOBIUM RESPIRATION EFFICIENCY 457 Oxygen Delivery and Other Possible Leghemoglobin Functions 457 The Soybean Symbiosis: Recognition of Efficient and Inefficient Phases of Bacteroid Respiration 459 Other Legume Symbioses: Evidence for Increasing Oxygen Tolerance 461 Respiration Substrate in Relation to Symbiotic Efficiency 466 Hemoglobin Nonlegume Symbioses 468 Rhizobium Nitrogen Fixation Without Leghemoglobin 470 CONCLUSIONS 471