Biomedical subjects

P Korber

Publications and source records attributed to P Korber.

4 recordsLinked to original sources

PubMed2000

Hsp15: a ribosome-associated heat shock protein.

We are analyzing highly conserved heat shock genes of unknown or unclear function with the aim of determining their cellular role. Hsp15 has previously been shown to be an abundant nucleic acid-binding protein whose synthesis is induced massively at the RNA level upon temperature upshift. We have now identified that the in vivo target of Hsp15 action is the free 50S ribosomal subunit. Hsp15 binds with very high affinity (K(D) <5 nM) to this subunit, but only when 50S is free, not when it is part of the 70S ribosome. In addition, the binding of Hsp15 appears to correlate with a specific state of the mature, free 50S subunit, which contains bound nascent chain. This provides the first evidence for a so far unrecognized abortive event in translation. Hsp15 is suggested to be involved in the recycling of free 50S subunits that still carry a nascent chain. This gives Hsp15 a very different functional role from all other heat shock proteins and points to a new aspect of translation.

Ammonium Chloride↗

PubMed2000

Structure of Hsp15 reveals a novel RNA-binding motif.

We have solved the crystal structure of the heat shock protein Hsp15, a newly isolated and very highly inducible heat shock protein that binds the ribosome. Comparison of its structure with those of two RNA-binding proteins, ribosomal protein S4 and threonyl-tRNA synthetase, reveals a novel RNA-binding motif. This newly recognized motif is remarkably common, present in at least eight different protein families that bind RNA. The motif's surface is populated by conserved, charged residues that define a likely RNA-binding site. An intriguing pattern emerges: stress proteins, ribosomal proteins and tRNA synthetases repeatedly share a conserved motif. This may imply a hitherto unrecognized functional similarity between these three protein classes.

Amino Acid Motifs↗

PubMed1999

A new heat shock protein that binds nucleic acids.

We describe the isolation of Hsp15, a new, very abundant heat shock protein that binds to DNA and RNA. Hsp15 is well conserved and related to a number of RNA-binding proteins, including ribosomal protein S4, RNA pseudouridine synthase, and tyrosyl-tRNA synthetase. The region shared between these proteins appears to represent a common, but previously unrecognized, RNA binding motif. Filter binding studies showed that Hsp15 binds to a 17-mer single-stranded RNA with a dissociation constant of 9 microM in 22.5 mM Hepes, pH 7. 0, 5 mM MgCl2. A role of Hsp15 in binding nucleic acids puts this protein into a different functional category from that of many other heat shock proteins that act as molecular chaperones or proteases on protein substrates.

Amino Acid Sequence↗

PubMed1995

Why is DsbA such an oxidizing disulfide catalyst?

DsbA, a member of the thioredoxin family of disulfide oxidoreductases, acts in catalyzing disulfide bond formation by donating its disulfide to newly translocated proteins. We have found that the two central residues within the active site Cys-30-Pro-31-His-32-Cys-33 motif are critical in determining the exceptional oxidizing power of DsbA. Mutations that change these two residues can alter the equilibrium oxidation potential of DsbA by more than 1000-fold. A quantitative explanation for the very high redox potential of DsbA was found by measuring the pKa of a single residue, Cys-30. The pKa of Cys-30 varied dramatically from mutant to mutant and could accurately predict the oxidizing power of each DsbA mutant protein.

Amino Acid Sequence↗