A Photolyase-Like Protein from Agrobacterium tumefaciens with an Iron-Sulfur Cluster

Abstract

Photolyases and cryptochromes are evolutionarily related flavoproteins with distinct functions. While photolyases can repair UV-induced DNA lesions in a light-dependent manner, cryptochromes regulate growth, development and the circadian clock in plants and animals. Here we report about two photolyase-related proteins, named PhrA and PhrB, found in the phytopathogen Agrobacterium tumefaciens. PhrA belongs to the class III cyclobutane pyrimidine dimer (CPD) photolyases, the sister class of plant cryptochromes, while PhrB belongs to a new class represented in at least 350 bacterial organisms. Both proteins contain flavin adenine dinucleotide (FAD) as a primary catalytic cofactor, which is photoreduceable by blue light. Spectral analysis of PhrA confirmed the presence of 5,10-methenyltetrahydrofolate (MTHF) as antenna cofactor. PhrB comprises also an additional chromophore, absorbing in the short wavelength region but its spectrum is distinct from known antenna cofactors in other photolyases. Homology modeling suggests that PhrB contains an Fe-S cluster as cofactor which was confirmed by elemental analysis and EPR spectroscopy. According to protein sequence alignments the classical tryptophan photoreduction pathway is present in PhrA but absent in PhrB. Although PhrB is clearly distinguished from other photolyases including PhrA it is, like PhrA, required for in vivo photoreactivation. Moreover, PhrA can repair UV-induced DNA lesions in vitro. Thus, A. tumefaciens contains two photolyase homologs of which PhrB represents the first member of the cryptochrome/photolyase family (CPF) that contains an iron-sulfur cluster.

Crystal structure of a prokaryotic (6-4) photolyase with an Fe-S cluster and a 6,7-dimethyl-8-ribityllumazine antenna chromophore

“…Several features are in support of a repair activity of CryB. It is required for the full in vivo photorepair in R. sphaeroides (12), as is PhrB in A. tumefaciens (7). Surface charge and DNA binding properties of CryB (10,11) are also compatible with DNA repair activity.…”

“…The genome of A. tumefaciens bears two genes encoding the photolyase-related proteins A and B (PhrA and PhrB) (7). PhrA is a prototypical CPD class III photolyase, whereas PhrB belongs to a group of photolyase-like proteins that has recently been denominated as iron-sulfur bacterial cryptochromes and photolyases (FeS-BCP) and is distantly related to other CPFs.…”

“…PhrA is a prototypical CPD class III photolyase, whereas PhrB belongs to a group of photolyase-like proteins that has recently been denominated as iron-sulfur bacterial cryptochromes and photolyases (FeS-BCP) and is distantly related to other CPFs. Mutant studies have shown that both PhrA and PhrB are required for the full photoreactivation in A. tumefaciens and that the roles of PhrA and PhrB with respect to in vivo DNA repair are not redundant (7). We therefore reasoned that PhrB could function as a (6-4) photolyase.…”

White collar 1‐induced photolyase expression contributes to UV ‐tolerance of Ustilago maydis

“…This is reminiscent, but not identical to the case of prokaryotic CPF proteins with iron–sulfur cluster (Oberpichler et al. ) where the absorption spectrum of FAD ox is superimposed on the spectrum of a cofactor later identified as 6,7‐dimethyl‐8‐ribityl‐lumazine (Geisselbrecht et al. ; Zhang et al.…”

Light-Dependent Functions of the Fusarium fujikuroi CryD DASH Cryptochrome in Development and Secondary Metabolism

“…The functional diversity of these photoreceptors became more evident when new members of this protein family were described in recent years, and cryptochromes are currently divided into at least seven subfamilies (49). One of the subfamilies comprises the cry-DASHs (50), widespread in photosynthetic organisms, but also found in some nonphotosynthetic bacteria, archaea, animals, and fungi.…”