The present disclosure provides light chain polypeptides that include a C-terminal extension, as well as antibodies and antibody conjugates containing such modified light chain polypeptides, where the C-terminal extension includes one or more cysteine residues. Conjugates that include an antibody of the present disclosure conjugated to an agent via the cysteine residue of the C-terminal amino acid extension are also provided. The present disclosure further provides nucleic acids encoding an antibody light chain polypeptide that includes a C-terminal amino acid extension including a cysteine residue. Pharmaceutical compositions including the antibodies or conjugates of the present disclosure are also provided, as are methods of making and use of the modified anti-bodies and conjugates of the present disclosure.
