Catalysis, commitment and encapsulation during GroE-mediated folding.

The Escherichia coli GroE chaperones assist protein folding under conditions where no spontaneous folding occurs. To achieve this, the cooperation of GroEL and GroES, the two protein components of the chaperone system, is an essential requirement. While in many cases GroE simply suppresses unspecific aggregation of non-native proteins by encapsulation, there are examples where folding is accelerated by GroE.

How chaperones fold proteins.

Chaperones are a functionally related group of proteins assisting protein folding in the cell under physiological and stress conditions. They share the ability to recognize and bind nonnative proteins thus preventing unspecific aggregation. The underlying functional principles of the different chaperone classes are beginning to be understood.

Solution structure of cytochrome c6 from the thermophilic cyanobacterium Synechococcus elongatus.

Cytochrome c6 is a small, soluble electron carrier between the two membrane-bound complexes cytochrome b6f and photosystem I (PSI) in oxygenic photosynthesis. We determined the solution structure of cytochrome c6 from the thermophilic cyanobacterium Synechococcus elongatus by NMR spectroscopy and molecular dynamics calculations based on 1586 interresidual distance and 28 dihedral angle restraints. The overall fold exhibits four alpha-helices and a small antiparallel beta-sheet in the vicinity of Met58, one of the axial heme ligands.

Sequence-specific resonance assignments of the 1H-NMR spectra and structural characterization in solution of the HIV-1 transframe protein p6.

The frameshift protein p6* encoded directly upstream of the protease in the human immunodeficiency virus type 1 (HIV-1) pol reading frame is thought to be a natural inhibitor of protease activation and to play a role in the polyprotein processing of Gag and Gag-Pol precursors. To allow structural characterization of the p6* transframe protein, the p6* coding region was cloned into the vector pGEX-KG and expressed in Escherichia coli as a fusion protein with glutathione S-transferase (GST) under the control of the tac promoter. Thrombin cleavage of the construct resulted in a 70-amino-acid polypeptide which is extended by two additional residues at the N-terminus compared to the natural p6* sequence.

Mutations that stabilize folding intermediates of phage P22 tailspike protein: folding in vivo and in vitro, stability, and structural context.

The folding of the trimeric phage P22 tailspike protein is affected by single amino acid substitutions designated temperature-sensitive folding (tsf) mutations. Their phenotypes are alleviated by two repeatedly isolated global suppressor (su) mutations (su V331A and su A334V) and by two additional substitutions (su V331G and su A334I), accessible through site-directed mutagenesis. We investigated the influence of the suppressor mutations on tailspike refolding in vitro, on its maturation at high expression levels in vivo, and on the rates of thermal unfolding of the native protein.