W0179

A Cell Wall Associated Protein from Staphylococcus aureus: Purification, Crystallization and Preliminary X-ray Analysis. Min Zhou^a, RongGuang Zhang^a, Grazyna Joachmiak^a, Piotr Gornicki^b, Olaf Schneewind^c and Andrzej Joachmiak^a, ^aBioscience Div., Structural Biology Center, Argonne National Laboratory, 9700 South Cass Av.e, Argonne, IL 60439, ^bDept. of Molecular Genetics and Cell Biology and ^cCommittee on Microbiology, Univ. of Chicago, 920 E. 58^th St., Chicago, IL 60637.

Surface proteins of Gram-positive bacteria play many important functions during the pathogenesis of human infections including colonization and evasion of host immune defenses, acquisition of nutrients for growth and proliferation, promotion bacterial adhesion to specific organ tissues, resistance to phagocytic killing and invasion of host cells. Staphylococcus aureus is a major pathogen involved in community- and hospital-acquired infections that has developed resistance to many antibiotics and is a growing public health concern. It produces numerous proteins involved in pathogenesis including toxins such as super-antigens that cause toxic-shock syndrome and staphylococcal scarlet fever. In attempt to identify potential new drug targets we have systematically pursued high throughput structure determination of gene products from S. aureus. To understand the mechanisms of heme-iron transport across cell wall, we have cloned and purified the proposed ATP-binding cassette transporter protein, which is one of the iron-regulated surface determinant (isd) locus of S. aureus. The protein was purified using automated procedures and crystallized by the hanging-drop vapor-diffusion method. Native crystals have been used as micro-seeds to obtain the crystals of Se-Met-labeled protein. The crystal belongs to P2₁2₁2₁ space group, with unit-cell parameters: a = 40.50 Å, b = 73.88 Å, c = 92.25 Å, α=β=γ=90^oand diffract to 1.8 Å using synchrotron radiation. In this report, the methodology used in protein and crystal production and the initial characterization of the protein crystals will be described and discussed.