PDBsum entry 1aa0

Attachment protein

PDB id: 1aa0

Contents

Protein chain

113 a.a.

Metals

_ZN

_CL

Waters ×240

References listed in PDB file

Key reference

• Title: Structure of bacteriophage t4 fibritin: a segmented coiled coil and the role of the c-Terminal domain.
• Authors: Y.Tao, S.V.Strelkov, V.V.Mesyanzhinov, M.G.Rossmann.
• Ref.: Structure, 1997, 5, 789-798. [DOI no: 10.1016/S0969-2126(97)00233-5]
• PubMed id: 9261070

Abstract

BACKGROUND: Oligomeric coiled-coil motifs are found in numerous protein structures; among them is fibritin, a structural protein of bacteriophage T4, which belongs to a class of chaperones that catalyze a specific phage-assembly process. Fibritin promotes the assembly of the long tail fibers and their subsequent attachment to the tail baseplate; it is also a sensing device that controls the retraction of the long tail fibers in adverse environments and, thus, prevents infection. The structure of fibritin had been predicted from sequence and biochemical analyses to be mainly a triple-helical coiled coil. The determination of its structure at atomic resolution was expected to give insights into the assembly process and biological function of fibritin, and the properties of modified coiled-coil structures in general. RESULTS: The three-dimensional structure of fibritin E, a deletion mutant of wild-type fibritin, was determined to 2.2 A resolution by X-ray crystallography. Three identical subunits of 119 amino acid residues form a trimeric parallel coiled-coil domain and a small globular C-terminal domain about a crystallographic threefold axis. The coiled-coil domain is divided into three segments that are separated by insertion loops. The C-terminal domain, which consists of 30 residues from each subunit, contains a beta-propeller-like structure with a hydrophobic interior. CONCLUSIONS: The residues within the C-terminal domain make extensive hydrophobic and some polar intersubunit interactions. This is consistent with the C-terminal domain being important for the correct assembly of fibritin, as shown earlier by mutational studies. Tight interactions between the C-terminal residues of adjacent subunits counteract the latent instability that is suggested by the structural properties of the coiled-coil segments. Trimerization is likely to begin with the formation of the C-terminal domain which subsequently initiates the assembly of the coiled coil. The interplay between the stabilizing effect of the C-terminal domain and the labile coiled-coil domain may be essential for the fibritin function and for the correct functioning of many other alpha-fibrous proteins.

Figure 5.
Figure 5. The C-terminal domain of fibritin E. (a) Stereo diagram of the C-terminal domain of a fibritin E subunit. The sidechains shown are those located in the hydrophobic interior formed at the interface between three symmetry-related subunits. The vertical line shows the trimer axis. Atoms are shown in standard colors. (b) Ribbon diagram of the C-terminal domain looking along the trimer axis, each subunit is shown in a different color. (c) Mainchain hydrogen bonds formed within the C-terminal domain of a fibritin E trimer. Parts (a) and (b) were drawn with MOLSCRIPT [43] and RASTER3D [44].

The above figure is reprinted by permission from Cell Press: Structure (1997, 5, 789-798) copyright 1997.

Secondary reference #1

• Title: Preliminary crystallographic studies of bacteriophage t4 fibritin confirm a trimeric coiled-Coil structure.
• Authors: S.V.Strelkov, Y.Tao, M.G.Rossmann, L.P.Kurochkina, M.M.Shneider, V.V.Mesyanzhinov.
• Ref.: Virology, 1996, 219, 190-194.
• PubMed id: 8623529

Secondary reference #2

• Title: Fibritin encoded by bacteriophage t4 gene wac has a parallel triple-Stranded alpha-Helical coiled-Coil structure.
• Authors: V.P.Efimov, I.V.Nepluev, B.N.Sobolev, T.G.Zurabishvili, T.Schulthess, A.Lustig, J.Engel, M.Haener, U.Aebi, Venyaminov syu.
• Ref.: J Mol Biol, 1994, 242, 470-486.
• PubMed id: 7932704