Preliminary crystallographic studies of two C-terminally truncated copper-containing nitrite reductases from : changed crystallizing behaviors caused by residue deletion

The C-terminal segment of copper-containing nitrite reductase from Achromobacter cycloclastes (AcNiR) has been found essential for maintaining both the quaternary structure and the enzyme activity of AcNiR. C-terminal despentapeptide AcNiR (NiRc-5) and desundecapeptide AcNiR (NiRc-11) are two important truncated mutants whose activities and stability have been affected by residue deletion. In this study, the two mutants were crystallized using the hanging drop vapor diffusion method. Crystals of NiRc-5 obtained at pH 5.0 and 6.2 both belonged to the P212121 space group with unit cell parameters a=99.0 Å, b=117.4 Å, c=122.8 Å (pH 5.0) and a=98.9Å, b=117.7Å, c=123.0Å (pH 6.2). NiRc-11 was crystallized in two crystal forms: the tetragonal form belonged to the space group P41 with a=b=96.0Å and c=146.6Å; the monoclinic form belonged to the space group P21 with a=86.0Å, b=110.1Å, c=122.7Å, and β=101.9°. The crystallizing behaviors of the two mutants differed from that of the native enzyme. Such change in combination with residue deletion is also discussed here.