Biosynthesis of the cyanobacterial reserve polymer multi-L-arginyl-poly-L-aspartic acid (cyanophycin): mechanism of the cyanophycin synthetase reaction studied with synthetic primers.
Biosynthesis of the cyanobacterial nitrogen reserve cyanophycin (multi-L-arginyl-poly-L-aspartic acid) is catalysed by cyanophycin synthetase, an enzyme that consists of a single kind of polypeptide. Efficient synthesis of the polymer requires ATP, the constituent amino acids aspartic acid and arginine, and a primer like cyanophycin. Using synthetic peptide primers, the course of the biosynthetic reaction was studied. The following results were obtained: (a) sequence analysis suggests that cyanophycin synthetase has two ATP-binding sites and hence probably two active sites; (b) the enzyme catalyses the formation of cyanophycin-like polymers of 25-30 kDa apparent molecular mass in vitro; (c) primers are elongated at their C-terminus; (d) the constituent amino acids are incorporated stepwise, in the order aspartic acid followed by arginine, into the growing polymer. A mechanism for the cyanophycin synthetase reaction is proposed; (e) the specificity of the enzyme for its amino-acid substrates was also studied. Glutamic acid cannot replace aspartic acid as the acidic amino acid, whereas lysine can replace arginine but is incorporated into cyanophycin at a much lower rate.
Berg
H
H
Biochemie der Pflanzen, Humboldt-Universität, Berlin, Germany; Universitätsklinikum Charité, Medizinische Immunologie, Berlin, Germany.
Ziegler
K
K
Piotukh
K
K
Baier
K
K
Lockau
W
W
Volkmer-Engert
R
R
D000255:Adenosine Triphosphate / Q000378:metabolism; D000595:Amino Acid Sequence; D001426:Bacterial Proteins; D001483:Base Sequence; D000458:Cyanobacteria / Q000378:metabolism; D011088:DNA Ligases / Q000378:metabolism; D017931:DNA Primers; D004591:Electrophoresis, Polyacrylamide Gel; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D010453:Peptide Synthases / Q000378:metabolism*; D010940:Plant Proteins / Q000096:biosynthesis* / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
D001426:Bacterial Proteins; D017931:DNA Primers; D010940:Plant Proteins; C024250:cyanophycin; D000255:Adenosine Triphosphate; D010453:Peptide Synthases; C113257:cyanophycin synthase, bacteria; D011088:DNA Ligases