N-terminal formylation of methionine is a unique protein modification found in prokaryotes, as well as in the mitochondria, chloroplasts, and even the cytosol of eukaryotic cells. Recent studies have revealed that human cells are capable of producing cytosolic proteins bearing N-terminal formylmethionine. This project aims to investigate N-terminal formylation-dependent interaction changes of the human tumor protein TPD54. Specifically, HeLa cells were transfected with TPD54-BirA*, along with either E. coli formyltransferase (EcFMT) or its catalytically inactive R43L mutant, to manipulate the formylation status.