Abstract
Long tail fibers of bacteriophage T4 are formed by proteins gp34, gp35, gp36, and gp37, with gp34 located at the phage-proximal end and gp37 at the phage-distal, receptor-binding end. We have solved the structure of the carboxy-terminal region of gp34, consisting of amino acids 894-1289, by single-wavelength anomalous diffraction and extended the structure to amino acids 744-1289 using data collected from crystals containing longer gp34-fragments. The structure reveals three repeats of a mixed α-β fibrous domain in residues 744 to 877. A triple-helical neck connects to an extended triple β-helix domain (amino acids 900-1127) punctuated by two β-prism domains. Next, a β-prism domain decorated with short helices and extended β-helices is present (residues 1146-1238), while the C-terminal end is capped with another short β-helical region and three β-hairpins. The structure provides insight into the stability of the fibrous gp34 protein.