Phosphorylation pattern of the NDUFS4 subunit of complex I of the mammalian respiratory chain.

Abstract The NDUFS4 subunit of complex I of the mammalian respiratory chain has a fully conserved carboxy-terminus with a canonical RVSTK phosphorylation site. Immunochemical analysis with specific antibodies shows that the serine in this site of the protein is natively present in complex I in both the phosphorylated and non-phosphorylated state. Two-dimensional IEF/SDS–PAGE electrophoresis, 32 P labelling and immunodetection show that “in vitro” PKA phosphorylates the serine in the C-terminus of the NDUFS4 subunit in isolated bovine complex I. 32 P labelling and TLC phosphoaminoacid mapping show that PKA phosphorylates serine and threonine residues in the purified heterologous human NDUFS4 protein.