Co-chaperonin GroES as a modulator of proteasomal activity.

The proteasome has a crucial part in the degradation of normal, damaged, mutant or misfolded proteins within both the ubiquitin ATP-dependent and the ubiquitin ATP-independent pathways. Proteasome-mediated proteolysis is modulated by diverse factors, and in this regard, chaperonins have been attracting great interest. The investigation on the role of a co-chaperonin, namely GroES, in the modulation of proteasomal activity was the focus of this work.

Mechanism of inhibition of wt-dihydrofolate reductase from E. coli by tea epigallocatechin-gallate.

Dihydrofolate reductase (DHFR) is a ubiquitous enzyme involved in major biological process, including DNA synthesis and cancer inhibition, and its modulation is the object of extensive structural, kinetic, and pharmacological studies. In particular, earlier studies showed that green tea catechins are powerful inhibitors of bovine liver and chicken liver DHFR. In this article, we report the results of inhibition kinetics for the enzyme from another source (DHFR from E.

Peroxynitrite-mediated oxidation of the C85S/C152E mutant of dihydrofolate reductase from Escherichia coli: functional and structural effects.

Peroxynitrite is a potent reactive oxygen species that is believed to mediate deleterious protein modifications in a wide variety of neurodegenerative disorders. In this study, we have analysed the effects of oxidative damage induced by peroxynitrite on a cysteine-free mutant of dihydrofolate reductase (SE-DHFR), from a functional and a structural point of view. The peroxynitrite-mediated oxidation results in the inhibition, concentration-dependent, of the catalytic activity.