Cover photograph (Copyright © 2004, American Society for Microbiology. All Rights Reserved.): Crystal structure of the 65-kDa heat shock protein of Mycobacterium tuberculosis reveals an unusual mode of oligomerization. The dimeric form might explain some of its observed immunological properties. Altered oligomerization of the protein leads to the loss of its ATPase activity and an altered chaperoning ability. (See related article on page 8105.)