Part of a lipoate-protein ligase complex that catalyzes both the ATP-dependent activation of exogenously supplied lipoate to lipoyl-AMP and the transfer of the activated lipoyl onto the lipoyl domains of lipoate-dependent enzymes. Can also use octanoate as substrate. (R)-lipoate + ATP + L-lysyl-[lipoyl-carrier protein] = (R)-N(6)-lipoyl-L-lysyl-[lipoyl-carrier protein] + AMP + diphosphate + H(+) Protein modification; protein lipoylation via exogenous pathway; protein N(6)-(lipoyl)lysine from lipoate: step 1/2. Protein modification; protein lipoylation via exogenous pathway; protein N(6)-(lipoyl)lysine from lipoate: step 2/2. Heterodimer composed of LplA and LplB. In contrast to E.coli, where the lipoate-protein ligase is encoded by a single gene product (LplA) with a large N-terminal domain and a small C-terminal domain, the same activity in T.acidophilum is dependent on two separate proteins, corresponding to the two domains of E.coli LplA, respectively.