Structural highlights
Function
[G3P_BPFD] Plays essential roles both in the penetration of the viral genome into the bacterial host via pilus retraction and in the extrusion process. During the initial step of infection, G3P mediates adsorption of the phage to its primary receptor, the tip of host F-pilus. Subsequent interaction with the host entry receptor tolA induces penetration of the viral DNA into the host cytoplasm. In the extrusion process, G3P mediates the release of the membrane-anchored virion from the cell via its C-terminal domain.[1] [2]
Publication Abstract from PubMed
The three disulfide bonds of the gene-3-protein of the phage fd are essential for the conformational stability of this protein, and it unfolds when they are removed by reduction or mutation. Previously, we used an iterative in vitro selection strategy to generate a stable and functional form of the gene-3-protein without these disulfides. It yielded optimal replacements for the disulfide bonds as well as several stabilizing second-site mutations. The best selected variant showed a higher thermal stability compared with the disulfide-bonded wild-type protein. Here, we investigated the molecular basis of this strong stabilization by solving the crystal structure of this variant and by analyzing the contributions to the conformational stability of the selected mutations individually. They could mostly be explained by improved side-chain packing. The R29W substitution alone increased the midpoint of the thermal unfolding transition by 14 deg and the conformational stability by about 25 kJ mol(-1). This key mutation (i) removed a charged side chain that forms a buried salt bridge in the disulfide-containing wild-type protein, (ii) optimized the local packing with the residues that replace the C46-C53 disulfide and (iii) improved the domain interactions. Apparently, certain residues in proteins indeed play key roles for stability.
Changing the determinants of protein stability from covalent to non-covalent interactions by in vitro evolution: a structural and energetic analysis.,Kather I, Jakob R, Dobbek H, Schmid FX J Mol Biol. 2008 Sep 12;381(4):1040-54. Epub 2008 Jul 2. PMID:18621056[3]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
See Also
References
- ↑ Deng LW, Perham RN. Delineating the site of interaction on the pIII protein of filamentous bacteriophage fd with the F-pilus of Escherichia coli. J Mol Biol. 2002 Jun 7;319(3):603-14. PMID:12054858 doi:http://dx.doi.org/10.1016/S0022-2836(02)00260-7
- ↑ Lorenz SH, Jakob RP, Weininger U, Balbach J, Dobbek H, Schmid FX. The Filamentous Phages fd and IF1 Use Different Mechanisms to Infect Escherichia coli. J Mol Biol. 2010 Nov 24. PMID:21110981 doi:10.1016/j.jmb.2010.11.030
- ↑ Kather I, Jakob R, Dobbek H, Schmid FX. Changing the determinants of protein stability from covalent to non-covalent interactions by in vitro evolution: a structural and energetic analysis. J Mol Biol. 2008 Sep 12;381(4):1040-54. Epub 2008 Jul 2. PMID:18621056 doi:10.1016/j.jmb.2008.06.073
