Crystallization and preliminary X-ray diffraction studies of infectious bronchitis virus nonstructural protein 9.

Avian infectious bronchitis virus (IBV), which causes respiratory disease in infected birds, belongs to coronavirus group 3. IBV encodes 15 nonstructural proteins (nsp2-nsp16) which play crucial roles in RNA transcription and genome replication. Nonstructural protein 9 (nsp9) has been identified as a protein that is essential to viral replication because of its single-stranded RNA-binding ability. The gene segment encoding IBV nsp9 has been cloned and expressed in Escherichia coli. The protein has been crystallized and the crystals diffracted X-rays to 2.44 A resolution. They belonged to the cubic space group I432, with unit-cell parameters a = b = c = 123.4 A, alpha = beta = gamma = 90 degrees . The asymmetric unit appeared to contain one molecule, with a solvent content of 62% (V(M) = 3.26 A(3) Da(-1)).