The Gag-Pol encoded proteinase of an avian retrovirus expressed in E. coli can produce a novel proteinase (PR + IleGly) that is two amino acids larger at its carboxy-terminal region than the major Gag proteinase (PR).
Gag-Pol frameshift translational products of avian retroviruses (e.g., myeloblastosis associated virus, MAV) contain a putative proteinase species of 131 amino acids that maps between the NC/PR and the PR/RT processing sites. Expression in Escherichia coli of an in-frame PR precursor that contains the natural NC/PR processing site and is translationally terminated at the PR/RT site leads to formation of a Gag-Pol proteinase of the expected molecular size (131 amino acids) and a novel PR product of 126 amino acids. This product extends 2 amino acids downstream of the gag-encoded 124 amino acids, and its proteolytic cleavage is promoted by conditions favorable for enzyme catalysis, is blocked by a specific MAV proteinase inhibitor, and can be demonstrated also for corresponding peptide substrates. The new self-processing cleavage product is termed PR(+IleGly) and exhibits similar, but slower, catalytic parameters than those of the Gag PR.
Brynda
J
J
Department of Gene Manipulation, Academy of Sciences of the Czech Republic, Prague.
Fábry
M
M
Horejsí
M
M
Sedlácek
J
J
D000595:Amino Acid Sequence; D016282:Aspartic Acid Endopeptidases / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D009189:Avian Myeloblastosis Virus / Q000201:enzymology* / Q000235:genetics; D001483:Base Sequence; D002384:Catalysis; D003001:Cloning, Molecular; D004926:Escherichia coli / Q000235:genetics; D015685:Fusion Proteins, gag-pol / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D007700:Kinetics; D008969:Molecular Sequence Data; D014176:Protein Biosynthesis; D011498:Protein Precursors / Q000235:genetics; D011499:Protein Processing, Post-Translational; D017421:Sequence Analysis; D013379:Substrate Specificity
D015685:Fusion Proteins, gag-pol; D011498:Protein Precursors; D016282:Aspartic Acid Endopeptidases; C036946:protease p15