Heteronuclear NMR studies of the specificity of the post-translational modification of biotinyl domains by biotinyl protein ligase

The lipoyl domains of 2-oxo acid dehydrogenase multienzyme complexes and th e biotinyl domains of biotindependent enzymes have homologous structures, b ut the target lysine residue in each domain is correctly selected for postt ranslational modification by lipoyl protein ligase and biotinyl protein lig ase, respectively. We have applied two-dimensional heteronuclear NMR spectr oscopy to investigate the interaction between the apo form of the biotinyl domain of the biotin carboxyl carrier protein of acetyl-CoA carboxylase and the biotinyl protein ligase (BPL) from Escherichia coli, Heteronuclear mul tiple quantum coherence NMR spectra of the N-15- labelled biotinyl domain w ere recorded in the presence and absence of the ligase and backbone amide H -1 and N-15 chemical shifts were evaluated. Small, but significant, changes in chemical shift were found in two regions, including the tight p-turn th at houses the lysine residue targetted for biotinylation, and the beta-stra nd 2 and the loop that precedes it in the domain. When compared with the th ree-dimensional structure, sequence alignments of other biotinyl and lipoyl domains, and mutagenesis data, these results give a clear indication of ho w the biotinyl domain is both recognised by BPL and distinguished from the structurally related lipoyl domain to ensure correct posttranslational modi fication. (C) 2000 Federation of European Biochemical Societies. Published br Elsevier Science B,V, All rights reserved.