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

The nemertean worm Cerebratulus lacteus neural tissue haemoglobin (109 amino acids, the shortest known haemoglobin) has been overexpressed in Escherichia coli, purified and crystallized. A highly redundant native data set has been collected at the Cu Kα wavelength to 2.05 Å resolution. The crystals belong to the orthorhombic P2₁2₁2₁ space group, with unit-cell parameters a = 42.5, b = 43.1, c = 60.2 Å and one molecule per asymmetric unit. The anomalous difference Patterson map clearly reveals the position of the haem Fe atom, thus paving the way for MAD/SAD structure determination.