Crystallization and preliminary X-ray analysis of neural haemoglobin from the nemertean worm Cerebratulus lacteus

The nemertean worm Cerebratulus lacteus neural tissue haemoglobin (109 amin o acids, the shortest known haemoglobin) has been overexpressed in Escheric hia coli, purified and crystallized. A highly redundant native data set has been collected at the Cu K alpha wavelength to 2.05 Angstrom resolution. T he crystals belong to the orthorhombic P2(1)2(1)2(1) space group, with unit -cell parameters a=42.5, b=43.1, c=60.2 Angstrom and one molecule per asymm etric unit. The anomalous difference Patterson map clearly reveals the posi tion of the haem Fe atom, thus paving the way for MAD/SAD structure determi nation.