This disclosure provides polypeptides comprising an antibody Fc region having a deletion of one or more cysteine residues in the hinge region and substitution with a sulfhydryl-containing residue of one or more CH3-interface amino acids. Also, provided are Fc-fusion proteins and antibodies containing said polypeptides, nucleic acids and vectors encoding said polypeptides, along with host cells and methods for making said polypeptides.