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H P Feng

Publications and source records attributed to H P Feng.

13 recordsLinked to original sources
PubMed2000

Structural insights into substrate binding by the molecular chaperone DnaK.

How substrate affinity is modulated by nucleotide binding remains a fundamental, unanswered question in the study of 70 kDa heat shock protein (Hsp70) molecular chaperones. We find here that the Escherichia coli Hsp70, DnaK, lacking the entire alpha-helical domain, DnaK(1-507), retains the ability to support lambda phage replication in vivo and to pass information from the nucleotide binding domain to the substrate binding domain, and vice versa, in vitro. We determined the NMR solution structure of the corresponding substrate binding domain, DnaK(393-507), without substrate, and assessed the impact of substrate binding. Without bound substrate, loop L3,4 and strand beta3 are in significantly different conformations than observed in previous structures of the bound DnaK substrate binding domain, leading to occlusion of the substrate binding site. Upon substrate binding, the beta-domain shifts towards the structure seen in earlier X-ray and NMR structures. Taken together, our results suggest that conformational changes in the beta-domain itself contribute to the mechanism by which nucleotide binding modulates substrate binding affinity.

Adenosine Triphosphatases↗
PubMed2000

Catching rays.

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Crystallography, X-Ray↗
PubMed1998

Molecular chaperones: clamps for the Clps?

The Clp/Hsp100 molecular chaperones are unusual in their ability to tease apart protein aggregates and complexes. Recent results make a good case that these chaperones bind substrates via PDZ-like domains; this may reflect a general strategy for manipulating the] assembly state of substrate proteins.

ATPases Associated with Diverse Cellular Activitie↗
PubMed1994

Kinetics of compaction during lysozyme refolding studied by continuous-flow quasielastic light scattering.

We recently developed an experiment, termed continuous-flow quasielastic light scattering (QLS), that is capable of monitoring the time evolution of the hydrodynamic diameter of macromolecules or macromolecular assemblies in solution. Here we report the use of this method to directly monitor the kinetics of compaction of the polypeptide chain of hen egg white lysozyme (HEWL) when protein refolding is initiated by 10-fold dilution from 5 M guanidine hydrochloride (GuHCl) at pH 1.5, 23 degrees C. Previously, such information could only be obtained indirectly, by analysis of the kinetics of binding ans release of a fluorescent probe dye. Refolding was also monitored by UV difference absorption spectroscopy to characterize the time scale of the formation of the native environment around the aromatic side chains under the same conditions used in the continuous-flow QLS experiments. We find that HEWL becomes compact within 1 s after the initiation of refolding, the shortest time that is accessible with our first-generation instrument. This time scale is shorter than that for the recovery of the native absorbances in the aromatic region. These results provide direct evidence that the intermediate on the folding pathway of lysozyme is compact. The implications of these results for models of protein folding are discussed.

Animals↗
PubMed1993

Lifetime of the histone octamer studied by continuous-flow quasielastic light scattering: test of a model for nucleosome transcription.

An instrument for continuous-flow quasielastic light scattering is described that allows the translational diffusion coefficient of macromolecules to be determined as a function of time after the initiation of some time-dependent process by mixing. Control experiments are carried out using the proteins lysozyme and BSA to verify that flow of the solution does not lead to erroneous results. The instrument is used to determine the lifetime of the histone octamer. A solution of octamer that is artificially stabilized in 2.0 M NaCl is rapidly diluted to physiological ionic strength, and the Stokes diameter is determined as a function of the time, delta t, after mixing. We find that the octamers dissociate into their component H2A-H2B heterodimers and H(3)2H4 tetramers on a time scale that is faster than the earliest time point for which data were obtained, 1 s after mixing. This result argues against a simple mechanism for the progression of RNA or DNA polymerase through chromatin.

Animals↗