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The DNA‐repair protein XPA is required to recognize a wide variety of bulky lesions during nucleotide excision repair. Independent NMR solution structures of a human XPA fragment comprising approximately 40% of the full‐length protein, the minimal DNA‐binding domain, revealed that one‐third of this molecule was disordered. To better characterize structural features of full‐length XPA, we performed time‐resolved trypsin proteolysis on active recombinant Xenopus XPA (xXPA). The resulting proteolytic fragments were analyzed by electrospray ionization interface coupled to a Fourier transform ion cyclotron resonance mass spectrometry and SDS‐PAGE. The molecular weight of the full‐length xXPA determined by mass spectrometry (30922.02 daltons) was consistent with that calculated from the sequence (30922.45 daltons). Moreover, the mass spectrometric data allowed the assignment of multiple xXPA …