The biosynthesis of multi-L-arginyl-poly(L-aspartic acid) in the filamentous cyanobacterium Anabaena cylindrica.
The cyanobacteria produce multi-L-arginyl-poly (aspartic acid), a high molecular weight (Mr=25 000-125 000) branched polypeptide consisting of a poly(aspartic acid) core with L-arginyl residues peptide bonded to each free carboxyl group of the poly(aspartic acid). An enzyme which will elongate Arg-poly(Asp) has been isolated and purified 92-fold from the filamentous cyanobacterium Anabaena cylindrica. The enzyme incorporates arginine and aspartic acid into Arg-poly(Asp) in a reaction which requires ATP, KCl, MgCl2, and a sulfhydryl reagent. The enzymatic incorporation of arginine is dependent upon the presence of L-aspartic acid but not visa versa, a finding which suggests the order of amino acid addition to the branched polypeptide-aspartic acid is added to the core followed by the attachment of an arginine branch. The elongation of Arg-poly(Asp) in-vitro is insensitive to the addition of protein synthesis inhibitors and to the addition of nucleases. These findings support the notion previosly suggested from in-vivo studies that Arg-poly(Asp) is synthesized via a non-ribosomal route and also demonstrate that amino-acetylated transfer-RNAs play no part in at least one step of the biosynthetic mechanism.
D001120:Arginine; D001224:Aspartic Acid; D000458:Cyanobacteria / Q000187:drug effects / Q000201:enzymology*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D010452:Peptide Biosynthesis; D010453:Peptide Synthases / Q000378:metabolism*; D011188:Potassium / Q000494:pharmacology; D013439:Sulfhydryl Reagents / Q000494:pharmacology; D013696:Temperature
D013439:Sulfhydryl Reagents; D001224:Aspartic Acid; D001120:Arginine; D010453:Peptide Synthases; D008274:Magnesium; D011188:Potassium