Kinetic and regiospecific interrogation of covalent intermediates in the nonribosomal peptide synthesis of yersiniabactin.
For interrogation of enzyme-bound intermediates in nonribosomal peptide synthetases (NRPSs), mass spectrometry is used to read out the kinetics and substrate specificity of this medicinally important class of enzymes. The protein HMWP2 (230 kDa) catalyzes 11 chemical reactions, four of which could be resolved by fast quench approaches combined with mass spectrometry. The rate of complex intermediate accumulation at the PCP1 active site was observed to occur with a rate of 19 s(-1), with the rate of cysteine acylation faster than that of intermediate translocation. Use of alternative substrates for salicylic acid (at the ArCP carrier domain) and l-cysteine (at the PCP1 carrier domain) revealed a high penalty for omission of the salicyl alcohol. For some substrates, large discrepancies were found between prior adenylation assays and the current MS-based readouts. Indirect evidence for condensation via a thiolate attack (vs an amino group) was also accumulated. This is the first report to correlate the percent occupancy of multiple active sites in parallel with kinetic and structural resolution of intermediates and provides new evidence of interdomain and intermodule communication within thiotemplate assembly lines.
Department of Chemistry, University of Illinois, Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, USA.
Shaun M
SM
McLoughlin
Neil L
NL
Kelleher
D000215:Acylation; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins / Q000378:metabolism*; D001665:Binding Sites; D003066:Coenzyme A Ligases / Q000378:metabolism; D003488:Cyanogen Bromide / Q000737:chemistry; D033862:Iron-Binding Proteins; D007700:Kinetics; D046908:Peptide Biosynthesis, Nucleic Acid-Independent; D010446:Peptide Fragments / Q000032:analysis / Q000378:metabolism; D010453:Peptide Synthases / Q000378:metabolism*; D033902:Periplasmic Binding Proteins; D010636:Phenols / Q000378:metabolism*; D021241:Spectrometry, Mass, Electrospray Ionization; D013379:Substrate Specificity; D013844:Thiazoles / Q000378:metabolism*
D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D033862:Iron-Binding Proteins; D010446:Peptide Fragments; D033902:Periplasmic Binding Proteins; D010636:Phenols; D013844:Thiazoles; C104398:yersiniabactin; D003066:Coenzyme A Ligases; C408477:YbtE protein, Yersinia pestis; D010453:Peptide Synthases; C104385:non-ribosomal peptide synthase; D003488:Cyanogen Bromide