The mismatch repair system of E. coli includes at least 12 protein components (Table) that function either in strand discrimination or in the repair process itself.

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#Id: 8935

#Unit 2. Cellular Organization

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#Id: 6731

#Unit 8. Inheritance Biology

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#Id: 10489

#Unit 4. Cell Communication and Cell Signaling

Cytotoxic T cells release granules containing the proteins perforin and granzyme-B

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#Id: 3359

#Unit 3. Fundamental Processes

Another example of direct reversal is the removal of the methyl group from the methylated base O6 –methylguanine  In this case, a methyltransferase removes the methyl group from the guanine residue by transferring it to one of its own cysteine residues. This is costly to the cell because the methyltransferase is not catalytic; having once accepted a methyl group, it cannot be used again.

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#Id: 1450

#Unit 4. Cell Communication and Cell Signaling

Ions, low-MW precursors of cellular macromolecules, products of intermediary metabolism, & small intracellular signaling molecules can pass from cell to cell through gap junctions.