The abundant DNA adduct -methyl deoxyguanosine contributes to miscoding during replication by human DNA polymerase η.

Aside from abasic sites and ribonucleotides, the DNA adduct -methyl deoxyguanosine ( -CH dG) is one of the most abundant lesions in mammalian DNA. Because -CH dG is unstable, leading to deglycosylation and ring-opening, its miscoding potential is not well-understood. Here, we employed a 2'-fluoro isostere approach to synthesize an oligonucleotide containing an analog of this lesion ( -CH 2'-F dG) and examined its miscoding potential with four Y-family translesion synthesis DNA polymerases (pols): human pol (hpol) η, hpol κ, and hpol ι and Dpo4 from the archaeal thermophile We found that hpol η and Dpo4 can bypass the -CH 2'-F dG adduct, albeit with some stalling, but hpol κ is strongly blocked at this lesion site, whereas hpol ι showed no distinction with the lesion and the control templates.

Mutual synergy between catalase and peroxidase activities of the bifunctional enzyme KatG is facilitated by electron hole-hopping within the enzyme.

KatG is a bifunctional, heme-dependent enzyme in the front-line defense of numerous bacterial and fungal pathogens against HO-induced oxidative damage from host immune responses. Contrary to the expectation that catalase and peroxidase activities should be mutually antagonistic, peroxidatic electron donors (PxEDs) enhance KatG catalase activity. Here, we establish the mechanism of synergistic cooperation between these activities.

A role for catalase-peroxidase large loop 2 revealed by deletion mutagenesis: control of active site water and ferric enzyme reactivity.

Catalase-peroxidases (KatGs), the only catalase-active members of their superfamily, all possess a 35-residue interhelical loop called large loop 2 (LL2). It is essential for catalase activity, but little is known about its contribution to KatG function. LL2 shows weak sequence conservation; however, its length is nearly identical across KatGs, and its apex invariably makes contact with the KatG-unique C-terminal domain.

Catalase in peroxidase clothing: Interdependent cooperation of two cofactors in the catalytic versatility of KatG.

Catalase-peroxidase (KatG) is found in eubacteria, archaea, and lower eukaryotae. The enzyme from Mycobacterium tuberculosis has received the greatest attention because of its role in activation of the antitubercular pro-drug isoniazid, and the high frequency with which drug resistance stems from mutations to the katG gene. Generally, the catalase activity of KatGs is striking.