Crystallization, preliminary X-ray analysis and molecular-replacement solution of the carboxy form of haemoglobin I from the fish Brycon cephalus

Haemoglobin, the 'honorary enzyme' [Brunori (1999), Trends Biochem. Sci. 24 , 158-161], constitutes a prime prototype for allosteric models. Here, the crystallization and preliminary X-ray analysis of haemoglobin I from the So uth American fish Brycon cephalus are reported. X-ray diffraction data have been collected to 2.5 Angstrom resolution using synchrotron radiation (LNL S). Crystals were determined to belong to the space group P6(1)22 and preli minary structural analysis revealed the presence of one dimer (alpha beta) in the asymmetric unit. The structure was determined using standard molecul ar-replacement techniques.