The disclosure provides constructs comprising a first fusion protein, a second fusion protein, and a linker, wherein the first fusion protein and the second fusion protein each include an affinity reagent and a reactive enzyme, and the linker includes a first and second functional groups specific for irreversibly inhibiting the first and second fusion protein reactive enzymes. The disclosure further provides a method including (a) contacting a first fusion protein including an affinity reagent and a reactive enzyme with a linker including a functional group specific for irreversibly inhibiting the first fusion protein reactive enzyme thereby coupling the first fusion protein and the linker, and (b) contacting a second fusion protein including an affinity reagent and a reactive enzyme with the linker, the linker including a functional group specific for irreversibly inhibiting the second fusion protein reactive enzyme thereby coupling the second fusion protein and the linker.
