CYSTALLIZATION AND CRYSTALLOGRAPHIC STUDIES OF BAR-HEADED GOOSE DEOXYHAEMOGLOBIN. Ziqian Hua*, Yiling Fang, Xiaoxi Zhou, Qian Xu, Bao Kuang, Xincheng Wei, Guangying Lu, Xiaocheng Gu, College of Life Sciences,Peking University, Beijing 100871 China

Bar-headed goose (Anser indicus) live and hatch their young at the west China's Qinhai lake, but at the end of autumn they migrate to the plains of northwest India. Flocks has been observed flying over the Himalayan Mountains at altitudes of about 9000 m where ambient pO₂ only have about 50 mmHg which accounts to 20% of pO₂ at sea level (Swan, L. A. 1970, Nat. Hist., 79, 68).

The Hbs from bar-headed goose shows more high oxygen affinity compared to closely related lowland species of goose, such as grelag goose. There are only four amino acid differences between the major Hb types of these two species, only one of which appears likely to effect oxygen affinity, the [[alpha]]l19 Pro matutes to Ala at [[alpha]]₁[[beta]]₁ interface(Oberthür, W., et al l982, Hoppe-seyler's Z. Physiol. Chem.,363, 581)

We have determined the X-ray crystallographic structure of bar-headed goose haemogloblin in the Oxy form to a resolution of 0.2 nm, Now we have got the crystals of deoxyHb and done the preliminary crystallographic studies in order to elucidate high oxygen affinity mechanism. DeoxyHb of bar-headed goose was prepared with Na₂S₂O₄ as reducing agent. The single crystals suitable for X-ray analysis have been grown from PEG 6000 at pH 7.2, protein 20 mg/ml with the hanging drop vappor diffusion method. DeoxyHb crystallizes in a Pl space group with lattice constants a=7.09 nm, b=9.54 nm, c=5.87 nm, the asymmetric unit has two molecules, Vm=0.256 nm³/Dal. The crystals diffract to about 0.23 nm resolution and 60% of X-ray diffraction data has been collected to 0.28 nm on X-200B Area Detector. A total of reflections is 30654, Rm=5.14% The determination of deoxyHb structure using the moleculer replacement method is in progress.