Altered dynamics of DNA bases adjacent to a mismatch: a cue for mismatch recognition by MutS.
ABSTRACT The structural deviations as well as the alteration in the dynamics of DNA at mismatch sites are considered to have a crucial role in mismatch recognition followed by its repair utilizing mismatch repair family proteins. To compare the dynamics at a mismatch and a non-mismatch site, we incorporated 2-aminopurine, a fluorescent analogue of adenine next to a G.T mismatch, a C.C mismatch, or an unpaired T, and at several other non-mismatch positions. Rotational diffusion of 2-aminopurine at these locations, monitored by time-resolved fluorescence anisotropy, showed distinct differences in the dynamics. This alteration in the motional dynamics is largely confined to the normally matched base-pairs that are immediately adjacent to a mismatch/ unpaired base and could be used by MutS as a cue for mismatch-specific recognition. Interestingly, the enhanced dynamics associated with base-pairs adjacent to a mismatch are significantly restricted upon MutS binding, perhaps "resetting" the cues for downstream events that follow MutS binding. Recognition of such details of motional dynamics of DNA for the first time in the current study enabled us to propose a model that integrates the details of mismatch recognition by MutS as revealed by the high-resolution crystal structure with that of observed base dynamics, and unveils a minimal composite read-out involving the base mismatch and its adjacent normal base-pairs.
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ABSTRACT: Sequence homologs of the small MutS-related (Smr) domain, the C-terminal endonuclease domain of MutS2, also exist as stand-alone proteins. In this study, we report the crystal structure of a proteolyzed fragment of YdaL (YdaL₃₉-₁₇₅), a stand-alone Smr protein from Escherichia coli. In this structure, residues 86-170 assemble into a classical Smr core domain and are embraced by an N-terminal extension (residues 40-85) with an α/β/α fold. Sequence alignment indicates that the N-terminal extension is conserved among a number of stand-alone Smr proteins, suggesting structural diversity among Smr domains. We also discovered that the DNA binding affinity and endonuclease activity of the truncated YdaL₃₉-₁₇₅ protein were slightly lower than those of full-length YdaL₁-₁₈₇, suggesting that residues 1-38 may be involved in DNA binding.Journal of Structural Biology 05/2011; 174(2):282-9. DOI:10.1016/j.jsb.2011.01.008 · 3.37 Impact Factor
Conference Paper: Design strategy for three-dimensional subband filter banks[Show abstract] [Hide abstract]
ABSTRACT: Since three-dimensional (3-D) subband coding has been introduced, most researches on 3-D subband coding perform temporal filtering first. In this paper, however, we investigate the best permutation strategy for temporal, vertical, and horizontal filtering to minimize the requirement of delay elements and find that the results are opposite to our expectationImage Processing, 1996. Proceedings., International Conference on; 10/1996