Structure of leghemoglobin

: The structure of the high spin complex of lupin leghemoglobin with acetate is refined at 2.0 A resolution using Diamond and Jack-Levitt technique (R=19%). The 0.05 A displacement of the iron atom from porphyrin plane to the distal side and the weakening of iron-nitrogen bond to the proximal histidine (2.37 A) give an explanation of the high affinity of the leghemoglobin for molecular oxygen. The ruffling of the porphyrin core may also favour it. Binding of nicotinate is accompanied by small conformational movements. Swinging out of the distal histidine from the heme pocket is the most prominent feature of this complex. The known amino acid sequences of leghemoglobin are analysed in view of the spatial structure of lupin hemoglobin.