Biomedical subjects

Ehud Gazit

Publications and source records attributed to Ehud Gazit.

40 records · Page 3Linked to original sources

PubMed2002

In vivo aggregation of a single enzyme limits growth of Escherichia coli at elevated temperatures.

The formation of protein aggregates is associated with unfolding and denaturation of proteins. Recent studies have indicated that, in Escherichia coli, cellular proteins tend to aggregate when the bacteria are exposed to thermal stress. Here, we show that the aggregation of one single E. coli cytoplasmic protein limits growth at elevated temperatures in minimal media. Homoserine trans-succinylase (HTS), the first enzyme in the methionine biosynthetic pathway, aggregates at temperatures higher than 44 degrees C in vitro. Above this temperature, we can also observe in vivo aggregation that results in the complete disappearance of the enzyme from the soluble fraction. Moreover, reducing the in vivo level of HTS aggregation enables growth at non-permissive temperatures. This is the first demonstration of the physiological role of aggregation of a specific protein in the growth of wild-type bacteria.

Acyltransferases↗

PubMed2002

Global analysis of tandem aromatic octapeptide repeats: the significance of the aromatic-glycine motif.

MOTIVATION: Tandem peptide repeats play a key role in self-assembly and aggregation processes. A notable example is the occurrence of tandem peptide repeats in prionic proteins and their role in the aggregation process that leads to the formation of the prion. One of the structural characteristics that is evident from the comparison of mammalian and yeast prion proteins is the presence of aromatic residues in their tandem repeats. These residues are accompanied by glycine residues before and/or after the aromatic amino acid. Such aromatic-glycine conjugates are also present in the tandem repeats of the large family of the bacterial ice nucleation proteins. To study the significance of such aromatic-glycine occurrences, a global analysis of all the aromatic octapeptide repeats in the Swiss-Prot and TrEMBL databases was conducted. The search pattern was formulated to compare the number of conjugates of each of the 20 natural amino acids before or after the different aromatic residues. RESULTS: The presence of aromatic-glycine conjugates appears to be significantly higher than aromatic conjugates to any other amino acid. Furthermore, all the six various combination of glycine occurrences before or after the three aromatic residues are present. No such pattern was observed for any other amino acid. The significance of the findings is being discussed in the context of the physicochemical properties of aromatic-glycine conjugates and its possible role in the facilitation of aggregates formation.

Amino Acid Motifs↗

PubMed2002

A possible role for pi-stacking in the self-assembly of amyloid fibrils.

Amyloid fibril formation is assumed to be the molecular basis for a variety of diseases of unrelated origin. Despite its fundamental clinical importance, the mechanism of amyloid formation is not fully understood. When we analyzed a variety of short functional fragments from unrelated amyloid-forming proteins, a remarkable occurrence of aromatic residues was observed. The finding of aromatic residues in diverse fragments raises the possibility that pi-pi interactions may play a significant role in the molecular recognition and self-assembly processes that lead to amyloid formation. This is in line with the well-known central role of pi-stacking interactions in self-assembly processes in the fields of chemistry and biochemistry. We speculate that the stacking interactions may provide energetic contribution as well as order and directionality in the self-assembly of amyloid structures. Experimental data regarding amyloid formation and inhibition by short peptide analogs also support our hypothesis. The pi-stacking hypothesis suggests a new approach to understanding the self-assembly mechanism that governs amyloid formation and indicates possible ways to control this process.

Alzheimer Disease↗

PubMed2002

Mechanistic studies of the process of amyloid fibrils formation by the use of peptide fragments and analogues: implications for the design of fibrillization inhibitors.

The process of amyloid fibrils formation is a common mechanism of a large number of unrelated infectious, genetic and spontaneous diseases. A partial list includes the bovine spongiform encephalopathy (BSE), Alzheimer's diseases, Type II diabetes, Creutzfeldt-Jakob disease, and various unrelated amyloidosis diseases. In spite of its significant clinical importance, the mechanism of fibrillization is not fully understood. This review discusses the recent advancements in the mechanistic studies of amyloid formation by the use peptide fragments and analogues of amyloid-forming proteins and polypeptides. The use of short peptide shed much light of the mechanism of amyloid fibrillization. Recent studies clearly prove that very short peptide fragments (as short as pentapeptides) can form well-ordered amyloidal structures. Therefore, the molecular recognition and self-assembly process that lead to the formation of order structures is being mediated by small structural elements. Analysis of short amyloid-related fragment by the use of an alanine-scan and sequence analysis of a variety of unrelated peptide and protein fragments suggest that aromatic interaction may play a central role in the process of amyloid formation. Inhibitors that are based on the short aromatic elements already demonstrated clear potency in arresting the process of amyloid fibrils formation. Taken together, the recent advancement in the mechanistic understanding of the process of amyloid fibrils formation has a major importance in the development of inhibitors of fibrillization that may serve as future therapeutic means to treat amyloid diseases.

Amyloid beta-Peptides↗