Characterization of the photolyase-like iron sulfur protein PhrB from Agrobacterium tumefaciens by Mossbauer spectroscopy

High field Mossbauer spectroscopy has been used to characterize the [4Fe-4S] (2 +)cluster of the protein PhrB from Agrobacterium tumefaciens which belongs to the cryptochrome/photolyase family (CPF) and which biological function has previously been shown to be DNA repair. Mossbauer spectra taken of the as prepared protein reveal delta = 0. 42 mms (- 1), and Delta E (Q) = 1. 26 mms (- 1)as well as an asymmetry parameter of eta = 0. 8. These parameters are characteristic for a ferredoxin-type [4Fe-4S] (2 +)cluster. In order to investigate whether this cluster is involved in DNA-repair the protein has also been studied in its photoactivated state during DNA binding. The so obtained data sets exhibit essentially the same Mossbauer parameters as those of the non-activated PhrB. This indicates that during DNA repair the [4Fe-4S] (2 +)cluster of PhrB has no significant amounts of transition states which have conformational changes compared to the resting state of the protein and which have life times of several seconds or longer.