On which amino-acids residue is the SDS acting on?
If your talking about Sodium Dodecyl Sulfate(a detergent) it has a two main functions:

(1) It disrupts all non-covalents bonds in proteins i.e hydrogen bonds from the main chain, or hydrogen bonds between residues which are dependent on protein shape.

(2) It coats the proteins with a negative charge which is useful for laboratory techniques such as gel electrophoresis.

Your question states "what amino acid residues does it act on?". You can be safe to assume that the SDS will coat the entire protein. About 0.1% SDS solution is enough to sature the polypetide chains of protein molcules with about one SDS molecule per two amino acid residues.