Disease relevance of PRB1

• We have cloned a gene, pepC, encoding a serine proteinase, PEPC, from Aspergillus niger by screening a phage lambda genomic DNA library with a gene (PRB1) from Saccharomyces cerevisiae which codes for proteinase YscB [1].

High impact information on PRB1

• Genetic analysis revealed that the accumulation of autophagic bodies in the vacuoles was the result of lack of the PRB1 product proteinase B, and disruption of the PRB1 gene confirmed this result [2].
• Antibodies raised against a synthetic peptide and an Escherichia coli-derived PRB1 open reading frame (ORF) protein cross-react with authentic protease B from yeast [3].
• Incubation in vitro of the LMr-precursor of proteinase yscB with mature proteinase yscA leads to further activation and to processing of the enzyme yielding the mature 33,000 Mr protein.(ABSTRACT TRUNCATED AT 250 WORDS)[4]
• Proteinase yscB transfers the intermediate mol. wt form of the original precursor to the apparently authentic, mature and active carboxypeptidase yscY [5].
• Prb1p promotes ALP maturation; overproduction of Prb1p accelerates ALP activation in detergent lysates but does not alter the measured kinetics of docking or fusion [6].

Biological context of PRB1

• Biogenesis of the yeast vacuole (lysosome). The use of active-site mutants of proteinase yscA to determine the necessity of the enzyme for vacuolar proteinase maturation and proteinase yscB stability [7].
• Consequences of growth media, gene copy number, and regulatory mutations on the expression of the PRB1 gene of Saccharomyces cerevisiae [8].
• Pro-proteinase yscB is converted to 5-10% to the mature enzyme, whereas procarboxypeptidase yscY is matured, although with reduced kinetics [9].
• We have isolated the structural gene, PRB1, for the vacuolar protease B of Saccharomyces cerevisiae from a genomic library by complementation of the prb1-1122 mutation [10].
• In the resulting episomal yeast expression plasmid pCNNmm5HT5A the modified 5HT5A gene is under the transcriptional control of the endopeptidase B gene promoter (PRB1) [11].

Anatomical context of PRB1

• In the presence of PMSF, wild-type cells accumulated autophagic bodies in the vacuoles under nutrient-deficient conditions in the same manner as did multiple protease-deficient mutants or cells with a disrupted PRB1 gene [2].
• The autocatalytic cleavage of the propeptide from Prb1p does not occur and Prb1p is rapidly degraded in the cytosol [12].

Associations of PRB1 with chemical compounds

• Little or no PRB1 mRNA is detectable during exponential growth on glucose as the carbon source; it begins to accumulate as cells exhaust the glucose [13].
• The study suggests that L. mexicana CPA and CPB perform similar roles to the aspartic peptidase PEP4 and the serine peptidase PRB1 in Saccharomyces cerevisiae [14].
• The codon of the catalytic serine in the active site of the vacuolar serine proteinase yscB (PrB) was changed to alanine, yielding the mutant gene prb1-Ala519 [15].
• When a multicopy PEP4 transformant of a prb1 mutant was grown in the presence of the aspartyl protease inhibitor pepstatin A, a significant level of proPrA was found in the growth medium [16].
• Degradation was not influenced by the vacuolar protease mutants Pep4p and Prb1p but was sensitive to the proteasome inhibitor lactacystin beta-lactone [17].

Regulatory relationships of PRB1

• Glucose-mediated repression of PRB1 is not subject to the same genetic controls as SUC2 [8].

Other interactions of PRB1

• However, mature proteinase yscB is not stable in the absence of proteinase yscA [7].
• Good nitrogen sources, like ammonia, repress PRB1 transcription; mutations in URE2 do not affect this response [13].
• Mutation of the HXK2 gene, which confers glucose-insensitive expression of secreted invertase, had no effect on PRB1 expression at the level of PrB activity [8].
• The phenotypic lag in the expression of the carboxypeptidase Y deficiency is abolished by nonsense mutations in either PRC1, the structural gene for carboxypeptidase Y, or PRB1, the structural gene for proteinase B. Models to explain these observations are proposed [18].
• The gene for proteinase yscB inhibitor I2B (PBI2) from Saccharomyces cerevisiae was isolated by oligonucleotide screening of a genomic DNA library, and was sequenced [19].

Analytical, diagnostic and therapeutic context of PRB1

• Following replacement of the wild-type PRB1 allele with prb1-Ala519, only a 73-kDa molecule was detected by immunoprecipitation with PrB-specific antiserum [15].

References