The pyridoxal 5’-phosphate-binding protein (PLPBP) is an evolutionary conserved protein linked to pyridoxal 5-phosphate (PLP) binding. Although mutations in PLPBP were shown to cause vitamin B6-dependent epilepsy, its cellular role and function remain elusive. We here report a detailed biochemical investigation of human PLPBP and its epilepsy-causing mutants evaluating stability, cofactor binding and oligomerization. In this context, chemical cross-linking combined with mass spectrometry unraveled an unexpected dimeric assembly of PLPBP. Furthermore, the interaction network of PLPBP was elucidated by chemical cross-linking paired with co-immunoprecipitation. Mass spectrometric analysis in a PLPBP knock-out cell line resulted in distinct proteomic changes compared to wild-type cells, including up-regulation of several cytoskeleton- and cell division-associated proteins. Finally, transfection experiments with vitamin B6-dependent epilepsy-causing PLPBP variants indicate a potential role of PLPBP in cell division, as well as proper muscle function. Taken together, our studies on the structure and cellular role of human PLPBP enable better understanding of physiological and pathological mechanism of this important protein.
Fux, A., Sieber, S.A., "Biochemical and proteomic studies of human pyridoxal 5’-phosphate-binding protein (PLPBP)", ACS Chem. Biol.