CRYSTALLIZATION AND PRELIMINARY X-RAY STUDIES OF TYPE A INFLUENZA VIRUS MATRIX PROTEIN M1. Bingdong Sha and Ming Luo, Center for Macromolecular Crystallography, Univ. of Alabama at Birmingham, Birmingham, AL 35294, USA

The matrix protein, M1, of influenza virus strain A/PR/8/34 has been purified from virions and crystallized. Influenza virus is a negative-strand RNA virus which is composed of eight single- stranded genomic segments coding for more than ten polypeptides. The matrix M1 protein(27Kd) is located as a bridge between the inner surface of the lipid bilayer of the virion envelope and the ribonucleocapsid protein(RNP) cores. The N-terminal of M1 protein has a hydrophobic domain which can be anchored in the virion lipid envelope to maintain the structural integrity of the virus particle. The C-terminal of M1 protein can be bound with RNP cores tightly to inhibit their transcription and replication. M1 can also determine the direction of RNP cores transport into or out of the nucleus. Upon entry of the virus into new host cell, M1 dissociates with RNP cores, allowing them to enter the nucleus. After transcription and replication, M1 induces the exit of RNP cores out of nucleus and prevents them from reentering the nucleus. M1 also plays a central role in virus assembly. The crystals consist of a stable C-terminal fragment(18Kd) of the M1 protein. We are also trying to get the crystals of N-terminal domain by subcloning. The typical crystal size is 0.05x0.05x0.2mm. The crystals diffracted X-ray to 2.35Å when X-rays from BNL synchrotron were used. X-ray diffraction studies indicated that the crystals have a space group of P3121 or P3221, with a=68.74Å, c=136.57Å. The suitable cryo-condition was also found in order to collet a whole data set from one single crystal. Vm calculations showed that there are two monomers in asymmetric unit. The successful crystallization of M1 protein will lead to the solution of the three- dimensional structure of the M1 protein.