CRYSTAL-STRUCTURE OF P22 TAILSPIKE PROTEIN - INTERDIGITATED SUBUNITS IN A THERMOSTABLE TRIMER

The tailspike protein (TSP) of Salmonella typhimurium phage P22 is a p art of the apparatus by which the phage attaches to the bacterial host and hydrolyzes the O antigen. It has served as a model system for gen etic and biochemical analysis of protein folding. The x-ray structure of a shortened TSP (residues 109 to 666) was determined to a 2.0 angst rom resolution. Each subunit of the homotrimer contains a large parall el beta helix. The interdigitation of the polypeptide chains at the ca rboxyl termini is important to protrimer formation in the folding path way and to thermostability of the mature protein.