Functional adaptation and its molecular basis in vertebrate hemoglobins, neuroglobins and cytoglobins

Hemoglobin (Hb), the paradigm for allosteric proteins through decades, has gained renaissance in recent years following discovery of globins or their genes in all living organisms and in all tissues of higher animals, and of new members of the globin family, such as neuroglobins, Ngb, found predominantly in neural and nerve tissues and cytoglobins, Cygb, that has unprecedented nuclear location. The recent progresses in this field have been prompted by the development of sophisticated techniques to probe molecular structure and functions, which have revealed novel functions, such as the scavenging and release of vasoactive nitric oxide and the regulation of cellular metabolism. This review deals with the functional adaptations and the underlying molecular mechanisms in globins and presents case examples of molecular adaptations encountered in vertebrates and agnathans.