3knq
From Proteopedia
Beta Turn Optimization of the Gene-3-Protein of Filamentous Phage Fd
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 PubMedIn the N2 domain of the gene-3-protein of phage fd, two consecutive beta-strands are connected by a mobile loop of seven residues (157-163). The stability of this loop is low, and the Asp160-Pro161 bond at its tip shows conformational heterogeneity with 90% being in the cis and 10% in the trans form. The refolding kinetics of N2 are complex because the molecules with cis or trans isomers at Pro161 both fold to native-like conformations, albeit with different rates. We employed consensus design to shorten the seven-residue irregular loop around Pro161 to a four-residue type I' turn without a proline. This increased the conformational stability of N2 by almost 10 kJ mol(-1) and abolished the complexity of the folding kinetics. Turn sequences obtained from in vitro selections for increased stability strongly resembled those derived from the consensus design. Two other type I' turns of N2 could also be stabilized by consensus design. For all three turns, the gain in stability originates from an increase in the rate of refolding. The turns form native-like structures early during refolding and thus stabilize the folding transition state. The crystal structure of the variant with all three stabilized turns confirms that the 157-163 loop was in fact shortened to a type I' turn and that the other turns maintained their type I' conformation after sequence optimization. Elimination of a cis-proline-containing loop and turn optimization stabilizes a protein and accelerates its folding.,Jakob RP, Zierer BK, Weininger U, Hofmann SD, Lorenz SH, Balbach J, Dobbek H, Schmid FX J Mol Biol. 2010 Jun 4;399(2):331-46. Epub 2010 Apr 13. PMID:20394751[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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