The present invention relates to Multifunctional Antibody Conjugates, comprising an antibody or antigen binding portion thereof, comprising at least a fragment of a light chain constant kappa region (CL&kgr；) comprising K188 according to Kabat numbering； a linker comprising the formula X-Y-Z, wherein Z is a group is covalently connected to the antibody through the side chain of K188, Y is a linear or branched biologically compatible connecting chain, and X is a group covalently connected to at least one Effector Moiety. The invention further provides specific MAC compounds and compositions of the invention.
