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Plant Physiol Biochem. 2005 Apr;43(4):309-13. Epub 2005 Mar 17.

DNA mismatch binding activities in Chlorella pyrenoidosa extracts and affinity isolation of G-T mismatch binding proteins.

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  • 1Institute of Bioscience and Biotechnology, National Taiwan Ocean University, Keelung 20224, Taiwan, ROC.


DNA mismatch recognition proteins contained in the extracts of unicellular alga Chlorella pyrenoidosa were isolated by affinity adsorption and 2-D gel electrophoresis. Incubation of the algal extracts with a 38-mer duplex oligonucleotide carrying a single DNA simple mispair generated a few gel retardation complexes. G-T mispair was recognized significantly better than C-T, G-G, G-A, and C-C mispairs by the algal extracts and these extracts bound very weakly to G-A and C-C mispairs, displaying a universal trend of mismatch binding efficiency. The levels of mismatch recognition complexes were slightly increased in the presence of 1 mM ATP. Two 13-kDa G-T binding polypeptides possessing pIs of 5.3 and 5.5 were isolated after resolving affinity-captured proteins by 2-D gel electrophoresis and the two factors were found to bind 5.5- and 2.8-fold stronger to heteroduplex than to homoduplex DNA, respectively. No proteins significantly homologous to the two algal G-T binding proteins were found by peptide mass fingerprinting (PMF). The sequence of a peptide generated from trypsin-cleavage of one G-T binding factor (pI 5.5) could be aligned with the amino acid sequences that form the C-terminal active sites of human and mouse mismatch-specific uracil/thymine-DNA glycosylases, suggesting the possibility of this factor as an algae- or a Chlorella-specific DNA mismatch glycosylase.

[PubMed - indexed for MEDLINE]
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