Similarities of the heme environment in vertebrate and non-vertebrate oxygen-binding hemoproteins

Abstract

In the search for structural features essential for the functional properties of oxygen binding, hemoproteins, hemoglobins and myoglobins from a great variety of species have been investigated. The results to date indicate that there is an essentially complete lack of conservation of amino acid sequence which would distinguish the oxygen-binding hemoproteins from hemoproteins with different functional properties [l-3]. On the other hand, the presently known X-ray data reveal closely related protein conformations in vertebrate and non-vertebrate hemoglobins and myoglobins [2,4-lo], indicating that invariant structural properties of oxygen-binding hemoproteins might be more clearly manifested in the three-dimensional arrangement of the protein than in the amino acid sequence. In this paper we report evidence obtained by high resolution proton nuclear magnetic resonance (NMR) spectroscopy that an aliphatic amino acid residue is located very close by to the distal side of the heme plane in chironomus hemoglobin and aplysia myoglobin. The same had previously been observed in single