Biomedical subjects

C J Penkett

Publications and source records attributed to C J Penkett.

4 recordsLinked to original sources

PubMed2000

Identification of residues involved in the interaction of Staphylococcus aureus fibronectin-binding protein with the (4)F1(5)F1 module pair of human fibronectin using heteronuclear NMR spectroscopy.

Many pathogenic Gram-positive bacteria express cell surface proteins that bind to components of the extracellular matrix. This paper describes studies of the interaction between ligand binding repeats (D3 and D1-D4) of a fibronectin-binding protein from Staphylococcus aureus with a module pair ((4)F1(5)F1) from the N-terminal region of fibronectin. When D3 was added to isotope-labeled (4)F1(5)F1, (1)H, (15)N, and (13)C NMR chemical shift changes indicate that binding is primarily via residues in (4)F1, although a few residues in (5)F1 are also affected. Both hydrophobic and electrostatic interactions appear to be involved. The NMR data indicate that part of the D3 repeat converts from a disordered to a more ordered, extended conformation on binding to (4)F1(5)F1. In further NMR experiments, selective reduction of the intensity of D1-D4 resonances was observed on binding to (4)F1(5)F1, consistent with previous suggestions that in each of D1, D2, and D3 repeats, the main fibronectin binding site is in the C-terminal region of the repeat. In D1-D4, these regions also appear to go from a disordered to a more ordered conformation of fibronectin binding. Although the regions of the two proteins which interact had been previously identified, the findings presented here identify, for the first time, the specific residues in both proteins that are likely to be involved in the interaction.

Adhesins, Bacterial↗

PubMed1999

Characterisation of side-chain conformational preferences in a biologically active but unfolded protein.

A combination of experimental NMR 3J alpha beta coupling constant measurements and theoretical predictions from a statistical model for a random coil have been used to characterise the conformations of amino acid side-chains in an unfolded fibronectin binding protein. The statistical model uses the distribution of torsion angles in a data base of native folded protein structures to provide a description of the torsion angle populations of each residue in a random coil. For all but three of the residues studied a close agreement is observed between the experimental 3J alpha beta data and the model predictions (correlation coefficient 0.90; RMSD 0.70 Hz). In these cases the populations about the chi 1 torsion angles in the conformational ensemble defining the fibronectin binding protein are well described by those present in the protein data base. For Phe 69, Asp 92 and Asp 105 however significant deviations are observed between the predictions and experimental data. Each of these side-chains is found to be involved in persistent non-random structural features arising from clustering of hydrophobic groups or interactions between charged side-chains. The analysis demonstrates the detailed insight that can be provided into conformationally disordered states by combining experimental and theoretical approaches.

Adhesins, Bacterial↗

PubMed1998

Structural and dynamical characterization of a biologically active unfolded fibronectin-binding protein from Staphylococcus aureus.

A 130-residue fragment (D1-D4) taken from a fibronectin-binding protein of Staphylococcus aureus, which contains four fibronectin-binding repeats and is unfolded but biologically active at neutral pH, has been studied extensively by NMR spectroscopy. Using heteronuclear multidimensional techniques, the conformational properties of D1-D4 have been defined at both a global and a local level. Diffusion studies give an average effective radius of 26.2 +/- 0.1 A, approximately 75% larger than that expected for a globular protein of this size. Analysis of chemical shift, 3JHNalpha coupling constant, and NOE data show that the experimental parameters agree well overall with values measured in short model peptides and with predictions from a statistical model for a random coil. Sequences where specific features give deviations from these predictions for a random coil have however been identified. These arise from clustering of hydrophobic side chains and electrostatic interactions between charged groups. 15N relaxation studies demonstrate that local fluctuations of the chain are the dominant motional process that gives rise to relaxation of the 15N nuclei, with a persistence length of approximately 7-10 residues for the segmental motion. The consequences of the structural and dynamical properties of this unfolded protein for its biological role of binding to fibronectin have been considered. It is found that the regions of the sequence involved in binding have a high propensity for populating extended conformations, a feature that would allow a number of both charged and hydrophobic groups to be presented to fibronectin for highly specific binding.

Adhesins, Bacterial↗

PubMed1997

NMR analysis of main-chain conformational preferences in an unfolded fibronectin-binding protein.

A 130-residue fragment of the Staphylococcus aureus fibronectin-binding protein has been found to exist in a highly unfolded conformation at neutral pH. Measurement of experimental NMR 3JHNalpha coupling constants provides evidence for individual residues having distinct main-chain conformational preferences that are dependent both on the amino acid concerned and on neighbouring residues in the sequence. Analysis shows that these variations in the populations of individual residues can be explained in detail in terms of statistical distributions of conformational states derived from the protein data base. In particular, when the preceding residue has a beta-branched or aromatic side-chain, a significant increase occurs in the population of the less sterically restricted b region of phi,psi space. The results indicate that the local structure of the fibronectin binding protein in solution, under conditions where it displays full activity, approximates very closely to a statistical random coil structure. This may be an important feature in the biological role of this and other polypeptides involved in protein-protein interactions.

Adhesins, Bacterial↗