9 research outputs found
Cloning and sequence analysis of cDNA for a human homolog of eubacterial ATP-dependent Lon proteases
AbstractOverlapping cDNA clones containing mRNA for a putative Lon protease (LonHS) were isolated from cDNA libraries prepared from human brain poly(A)+ RNA. The determined nucleotide sequence contains a 2814-bp open reading frame with two potential initiation codons (positions 62–64 and 338–340). The 5'-terminal 337-nucleotide fragment of LonHS mRNA is highly enriched with G and C nucleotides and could direct synthesis of the LonHS N-terminal domain. More likely this region promotes initiation of protein synthesis from the second AUG codon in a cap-independent manner. The amino acid sequence initiated at the second AUG codon includes 845 residues, over 30% of which are identical to those of eubacterial Lon proteases. Residues of the ‘A’ and ‘B’ motifs of NTP-binding pattern and a plausible catalytic serine residue are conserved in LonHS. Northern blot analysis revealed LonHS mRNA in lung, duodenum, liver and heart, but not in thymus cells
Targeting Cullin–RING E3 ubiquitin ligases for drug discovery: structure, assembly and small-molecule modulation
Chalcone-based small-molecule inhibitors attenuate malignant phenotype via targeting deubiquitinating enzymes
Cloning of cDNA for granzyme-like protein III, a novel serine proteinase from rat duodenum
Identification, sequence analysis, and characterization of cDNA clones encoding two granzyme-like serine proteinases from rat duodenum
The Saccharomyces cerevisiae ubiquitin-proteasome system
Our studies of the yeast ubiquitin-proteasome pathway have uncovered a number of general principles that govern substrate selectivity and proteolysis in this complex system. Much of the work has focused on the destruction of a yeast transcription factor, MAT alpha 2. The alpha 2 protein is polyubiquitinated and rapidly degraded in alpha-haploid cells. One pathway of proteolytic targeting, which depends on two distinct endoplasmic reticulum-localized ubiquitin-conjugating enzymes, recognizes the hydrophobic face of an amphipathic helix in alpha 2. Interestingly, degradation of alpha 2 is blocked in a/alpha-diploid cells by heterodimer formation between the alpha 2 and a1 homeodomain proteins. The data suggest that degradation signals may overlap protein-protein interaction surfaces, allowing a straightforward steric mechanism for regulated degradation. Analysis of alpha 2 degradation led to the identification of both 20S and 26S proteasome subunits, and several key features of proteasome assembly and active-site formation were subsequently uncovered. Finally, it has become clear that protein (poly) ubiquitination is highly dynamic in vivo, and our studies of yeast de-ubiquitinating enzymes illustrate how such enzymes can facilitate the proteolysis of diverse substrates