The T-synthase is the key beta 3-galactosyltransferase essential for biosynthesis of core 1 O-glycans (Gal beta 1-3GalNAc alpha 1-Ser/Thr) in animal cell glycoproteins. Here we describe the novel ability of an endoplasmic reticulum-localized molecular chaperone termed Cosmc to specifically interact with partly denatured T-synthase in vitro to cause partial restoration of activity. By contrast, ...

Induction of transcription of the GAL genes of yeast by galactose is a multistep process: Galactose frees the activator Gal4 of its inhibitor, Gal80, allowing Gal4 to recruit proteins required to transcribe the GAL genes. Here, we show that deletion of components of either the HSP90 or the HSP70 chaperone machinery delays this induction. This delay remains when the galactose-signaling pathway i...

α-Crystallin is a small heat shock protein and molecular chaperone. Binding of Cu2+ and Zn2+ ions to α-crystallin leads to enhanced chaperone function. Sequestration of Cu2+ by α-crystallin prevents metal-ion mediated oxidation. Here we show that binding of human γD-crystallin (HGD, a natural substrate) to human αA-crystallin (HAA) is inversely related to the binding of Cu2+/Zn2+ ions: The high...

α-Crystallin, a small heat shock protein (sHSP), constitutes the major portion of eye lens cytoplasm and its concentration in the lens can reach up to 50% of the total protein. Like other sHSP, α-crystallin displays chaperone-like activity in suppressing the aggregation of various proteins and in preventing inactivation of enzymes due to heat and other stress conditions [1-6]. Hence, in additio...

Wild-type p53 is a short-lived protein which turns over very rapidly via selective proteolysis in the ubiquitin-proteasome pathway. Most p53 mutations, however, encode for protein products which display markedly increased intracellular levels and are associated with positive tumor-promoting activity. The mechanism by which mutation leads to impairment of ubiquitination and proteasome-mediated d...

Experimental study of the role of disorder in protein function is challenging. It has been proposed that proteins utilize disordered regions in the adaptive recognition of their various binding partners. However apart from a few exceptions, defining the importance of disorder in promiscuous binding interactions has proven to be difficult. In this paper, we have utilized a genetic selection that...

Compared with other chaperone systems, heat shock proteins Hsp70 and Hsp90 interact with a larger variety of co-chaperone proteins that regulate their activity or aid in the folding of specific substrate proteins. Although many co-chaperones are soluble cytosolic proteins, co-chaperone domains are also found in modular adaptor proteins, which are often localized to intracellular membranes or el...

DsbG, a protein disulfide isomerase present in the periplasm of Escherichia coli, is shown to function as a molecular chaperone. Stoichiometric amounts of DsbG are sufficient to prevent the thermal aggregation of two classical chaperone substrate proteins, citrate synthase and luciferase. DsbG was also shown to interact with refolding intermediates of chemically denatured citrate synthase and p...

SecB chaperones assist protein export in bacteria. However, certain SecB family members have diverged to become specialized toward the control of toxin-antitoxin (TA) systems known to promote bacterial adaptation to stress and persistence. In such tripartite TA-chaperone (TAC) systems, the chaperone was shown to assist folding and to prevent degradation of its cognate antitoxin, thus facilitati...

Chemical arrays were employed to screen ligands for HtpG, the prokaryotic homologue of Hsp (heat-shock protein) 90. We found that colistins and the closely related polymyxin B interact physically with HtpG. They bind to the N-terminal domain of HtpG specifically without affecting its ATPase activity. The interaction caused inhibition of chaperone function of HtpG that suppresses thermal aggrega...