Preliminary X-ray diffraction analysis of crystals of the PII protein from Escherichia coli.

PII protein, which carries metabolic signals regulating the transcription and activity of glutamine synthetase in nitrogen assimilation in Escherichia coli, has been crystallized in space group P2(1) with a = 47.8 A, b = 62.9 A, c = 52.8 A and beta = 100.3 degrees and space group P2(1)2(1)2(1) with a = 52.2 A. b = 64.9 A and c = 100.1 A. Both the monoclinic crystals, which diffract beyond 3.0 A, and the orthorhombic crystals, which diffract beyond 2.5 A, probably have three molecules of 12,400 Da each in the crystallographic asymmetric unit.