Initiation of Phage Infection by Partial Unfolding and Prolyl Isomerization

Abstract

Background: Bacteriophage fd is activated for infection by partial unfolding and prolyl isomerization. Results: NMR spectroscopy localized Pro-213-coupled unfolding to regions of the interdomain hinge of the phage gene-3-protein.Conclusion: Pro-213 regulates phage infectivity by a specific long-range effect on the conformational stability of the gene-3-protein.Significance: A proline switch controls the biological function in a remote part of a protein.

Molecular Determinants of a Regulatory Prolyl Isomerization in the Signal Adapter Protein c-CrkII

“…In the cis form, the affinity for the substrate peptide was decreased but not abolished. The trans → cis isomerization at Pro238 is not followed by tight domain association and complete inhibition of substrate binding, as observed previously for a proline switch in a phage infection protein. − The cis Pro238 form of c-CrkII is thus not a fully autoinhibited state but a low-affinity state. The lack of a tight domain docking reaction explains why a mutual stabilization of the two domains in the SH3 N –SH3 C protein was not detected in the folding studies.…”

“…In the infection protein of phage fd, binding to a bacterial pilus creates a signal that is propagated via the unfolding of an interdomain hinge to a proline, and the switching rate is set by the local sequence around this proline. 21,22 In c-CrkII, it remains to be elucidated how the cis−trans isomerization at Pro238 is initiated, how the cis−trans equilibrium is shifted, and how the lifetime of the open form is regulated. In human and chicken c-CrkII, Tyr222 can be phosphorylated by kinases such as Abl, and this phosphorylation might influence Pro238 isomerization, as well.…”

Real-time NMR monitoring of biological activities in complex physiological environments

“…Proline isomerization is invisible to most biochemical methods, however, NMR provides a powerful probe for this structural interconversion, and RT-NMR recently elucidated a role for proline isomerization in gene-3-protein (G3P) in filamentous phage infection [38]. The application of RT-NMR to monitor proline isomerization in protein folding studies was recently reviewed by Kumar and Balbach [39].…”

Bacterial sensing of bacteriophages in communities: the search for the Rosetta stone

“…This signal may be propagated to neighboring receptors via conformational changes, decreasing availability for irreversible binding. Another possible mechanism can be extrapolated from the recent identification of the molecular mechanism underlying the binding of the filamentous bacteriophage fd to the bacterial pilus, coupling unfolding and the prolyl isomerization of viral protein Gp3 [5]. The partially unfolded Gp3 uncovers the binding site for bacterial protein TolA, the secondary receptor.…”