CRYSTALLIZATION AND PRELIMINARY-X-RAY ANALYSIS OF THE DSDNA BACTERIOPHAGE-HK97 MATURE EMPTY CAPSID

HK97 is a temperate dsDNA bacteriophage of Escherichia coil that is st ructurally similar to phage lambda, with an icosahedral head of triang ulation (T) number 7. Although the capsids of several large dsDNA phag es have been studied extensively using a variety of biophysical approa ches, no high-resolution structure is available. We have grown crystal s of mature but empty bacteriophage HK97 capsids that diffract to at l east 3.5 Angstrom using synchrotron radiation. The HK97 Head II crysta ls are the first capsid crystals from a dsDNA bacteriophage that diffr act X-rays to high resolution. A capsid precursor (prohead) was made i n vivo by expressing capsid proteins in E. coil. This prohead was puri fied, converted to Head II in vitro, and used to grow crystals. The em pty Head II has the same form as the mature HK97 capsid, but without D NA. The crystals were grown in a mixture of ammonium sulfate and PEG 8 000, directly in an X-ray capillary to minimize crystal handling, The unit cell is monoclinic, with dimensions a = 580 Angstrom, b = 625 Ang strom, c = 790 Angstrom, beta = 90.0 degrees and two particles per uni t cell. (C) 1998 Academic Press.