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A New Cofactor in a Prokaryotic Enzyme: Tryptophan Tryptophylquinone as the Redox Prosthetic Group in Methylamine Dehydrogenase

McIntire, William S. and Wemmer, David E. and Chistoserdov, Andrei and Lidstrom, Mary E. (1991) A New Cofactor in a Prokaryotic Enzyme: Tryptophan Tryptophylquinone as the Redox Prosthetic Group in Methylamine Dehydrogenase. Science, 252 (5007). pp. 817-824. ISSN 0036-8075. doi:10.1126/science.2028257.

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Methylamine dehydrogenase (MADH), an α_2β_2 enzyme from numerous methylotrophic soil bacteria, contains a novel quinonoid redox prosthetic group that is covalently bound to its small beta subunit through two amino acyl residues. A comparison of the amino acid sequence deduced from the gene sequence of the small subunit for the enzyme from Methylobacterium extorquens AM1 with the published amino acid sequence obtained by the Edman degradation method, allowed the identification of the amino acyl constituents of the cofactor as two tryptophyl residues. This information was crucial for interpreting ^1H and ^(13)C nuclear magnetic resonance, and mass spectral data collected for the semicarbazide- and carboxymethyl-derivatized bis(tripeptidyl)-cofactor of MADH from bacterium W3A1. The cofactor is composed of two cross-linked tryptophyl residues. Although there are many possible isomers, only one is consistent with all the data: The first tryptophyl residue in the peptide sequence exists as an indole-6,7-dione, and is attached at its 4 position to the 2 position of the second, otherwise unmodified, indole side group. Contrary to earlier reports, the cofactor of MADH is not 2,7,9-tricarboxypyrroloquinoline quinone (PQQ), a derivative thereof, or pro-PQQ. This appears to be the only example of two cross-linked, modified amino acyl residues having a functional role in the active site of an enzyme, in the absence of other cofactors or metal ions.

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Additional Information:© 1991 American Association for the Advancement of Science. Received 25 January 1991; accepted 19 March 1991. We thank J. Leary for measuring the exact [M+H+] mass of the bis(tripeptidyl) cofactor, P. F. Knowles and J. Sanders-Loehr for prepublication copies of their manuscripts, and L. Chen, V. L. Davidson, H. Duine, W. Hol, F. S. Mathews, E. G. Huizinga, and F. M. D. Villieux for their input and cooperation in the preparation of this manuscript. We also thank J. P. Klinman, C. Hartmann, and D. M. Dooley for support, discussions, and suggestions throughout the research. Funded by the Department of Veterans Affairs, NIH Program Project grant no. HL 16251, NSF grant DMB 87-18741 (W.S.M.), the Office of Energy Research, Office of Health Environment Research, Health Effects Research Division of the USDOE, contract DE AC03-76SF00098, instrumentation funding from USDOE grant DE FG05-86ER75281, NSF grants DMB 86-09035 and BBS 87-20134 (D.E.W.), and NIH grant GM 36296 (M.E.L.).
Funding AgencyGrant Number
Department of Veterans AffairsUNSPECIFIED
NIHHL 16251
NSFDMB 87-18741
Department of Energy (DOE)DE AC03-76SF00098
Department of Energy (DOE)FG05-86ER75281
NSFDMB 86-09035
NSFBBS 87-20134
NIHGM 36296
Issue or Number:5007
Record Number:CaltechAUTHORS:20150107-125823717
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Official Citation:A new cofactor in a prokaryotic enzyme: tryptophan tryptophylquinone as the redox prosthetic group in methylamine dehydrogenase WS McIntire, DE Wemmer, A Chistoserdov, and ME Lidstrom Science 10 May 1991: 252 (5007), 817-824. [DOI:10.1126/science.2028257]
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:53284
Deposited By: Tony Diaz
Deposited On:08 Jan 2015 02:54
Last Modified:10 Nov 2021 20:00

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