Heme proteins: Hemoglobin

Abstract

Progress in understanding structure and function of heme proteins has been so great during the past ten years that it is difficult to review it with any completeness*. The field has been and still is among the most active ones in Biochemistry not only for the physiological interest but also because heme proteins, particularly hemoglobin, have been taken as a prototype for studying (in general) function-structure relationships in proteins and the basic mechanisms underlying biological regulation at a molecular level. The present review will be largely confined to hemoglobin and even so there will be many omissions and some important contributions may be neglected. Substantial progress has also been made in’ the elucidation of structure and reactivities of cytochromes, cytochrome oxidase and other heme proteins, but even a short mention of the main results in these areas would take up too much space. Naturally, the development of the subject in the last decade has depended heavily on previous basic achievements, primarily on the initial determinations of the structures of myoglobin [5] and hemoglobin [6] by X-ray analysis. On these bases, many of the questions which have lately been answered, were clearly posed about ten years ago:With hemoglobin, some of the unanswered problems at the time were: The resolution of the structures of the ligand-bound and the ligand-free proteins at an atomic level; the structural details of the conformation change associated with ligand binding, the mechanism by which it was produced, and in turn, how this