Publications

• Interaction of PqqE and PqqD in the pyrroloquinoline quinone (PQQ) biosynthetic pathway links PqqD to the radical SAM superfamily.

  Wecksler S.R., Stoll S., Iavarone A.T., Imsand E.M., Tran H., Britt R.D., Klinman J.P.

  pqqD is one of six genes required for PQQ production in Klebsiella pneumoniae. Herein, we demonstrate that PqqD interacts specifically with the radical SAM enzyme PqqE, causing a perturbation in the electronic environment around the [4Fe-4S](+) clusters. This interaction redirects the role for Pqq ... >> More

  pqqD is one of six genes required for PQQ production in Klebsiella pneumoniae. Herein, we demonstrate that PqqD interacts specifically with the radical SAM enzyme PqqE, causing a perturbation in the electronic environment around the [4Fe-4S](+) clusters. This interaction redirects the role for PqqD in PQQ biosynthesis. << Less

  Chem. Commun. (Camb.) 46:7031-7033(2010) [PubMed] [EuropePMC]

• PqqD is a novel peptide chaperone that forms a ternary complex with the radical S-adenosylmethionine protein PqqE in the pyrroloquinoline quinone biosynthetic pathway.

  Latham J.A., Iavarone A.T., Barr I., Juthani P.V., Klinman J.P.

  Pyrroloquinoline quinone (PQQ) is a product of a ribosomally synthesized and post-translationally modified pathway consisting of five conserved genes, pqqA-E. PqqE is a radical S-adenosylmethionine (RS) protein with a C-terminal SPASM domain, and is proposed to catalyze the formation of a carbon-c ... >> More

  Pyrroloquinoline quinone (PQQ) is a product of a ribosomally synthesized and post-translationally modified pathway consisting of five conserved genes, pqqA-E. PqqE is a radical S-adenosylmethionine (RS) protein with a C-terminal SPASM domain, and is proposed to catalyze the formation of a carbon-carbon bond between the glutamate and tyrosine side chains of the peptide substrate PqqA. PqqD is a 10-kDa protein with an unknown function, but is essential for PQQ production. Recently, in Klebsiella pneumoniae (Kp), PqqD and PqqE were shown to interact; however, the stoichiometry and KD were not obtained. Here, we show that the PqqE and PqqD interaction transcends species, also occurring in Methylobacterium extorquens AM1 (Me). The stoichiometry of the MePqqD and MePqqE interaction is 1:1 and the KD, determined by surface plasmon resonance spectroscopy (SPR), was found to be ∼12 μm. Moreover, using SPR and isothermal calorimetry techniques, we establish for the first time that MePqqD binds MePqqA tightly (KD ∼200 nm). The formation of a ternary MePqqA-D-E complex was captured by native mass spectrometry and the KD for the MePqqAD-MePqqE interaction was found to be ∼5 μm. Finally, using a bioinformatic analysis, we found that PqqD orthologues are associated with the RS-SPASM family of proteins (subtilosin, pyrroloquinoline quinone, anaerobic sulfatase maturating enzyme, and mycofactocin), all of which modify either peptides or proteins. In conclusion, we propose that PqqD is a novel peptide chaperone and that PqqD orthologues may play a similar role in peptide modification pathways that use an RS-SPASM protein. << Less

  J. Biol. Chem. 290:12908-12918(2015) [PubMed] [EuropePMC]

• Demonstration that the radical S-adenosylmethionine (SAM) enzyme PqqE catalyzes de novo carbon-carbon cross-linking within a peptide substrate PqqA in the presence of the peptide chaperone PqqD.

  Barr I., Latham J.A., Iavarone A.T., Chantarojsiri T., Hwang J.D., Klinman J.P.

  The radical S-adenosylmethionine (SAM) protein PqqE is predicted to function in the pyrroloquinoline quinone (PQQ) biosynthetic pathway via catalysis of carbon-carbon bond formation between a glutamate and tyrosine side chain within the small peptide substrate PqqA. We report here that PqqE activi ... >> More

  The radical S-adenosylmethionine (SAM) protein PqqE is predicted to function in the pyrroloquinoline quinone (PQQ) biosynthetic pathway via catalysis of carbon-carbon bond formation between a glutamate and tyrosine side chain within the small peptide substrate PqqA. We report here that PqqE activity is dependent on the accessory protein PqqD, which was recently shown to bind PqqA tightly. In addition, PqqE activity in vitro requires the presence of a flavodoxin- and flavodoxin reductase-based reduction system, with other reductants leading to an uncoupled cleavage of the co-substrate SAM. These results indicate that PqqE, in conjunction with PqqD, carries out the first step in PQQ biosynthesis: a radical-mediated formation of a new carbon-carbon bond between two amino acid side chains on PqqA. << Less

  J. Biol. Chem. 291:8877-8884(2016) [PubMed] [EuropePMC]