Carrier protein that bears the covalently bound substrates for lysine biosynthesis; the bound alpha-aminoadipate (AAA) is sequentially converted to L-lysine. Amino-acid biosynthesis; L-lysine biosynthesis via AAA pathway. Formation of an isopeptide bond between the gamma-carboxyl group of the C-terminal glutamate and the amino group of alpha-aminoadipate (AAA) is catalyzed by LysX. The bound AAA is then converted to L-lysine in a series of reactions catalyzed by LysZ, LysY and LysJ. Release of the product L-lysine is catalyzed by LysK (PubMed:19620981). The purified protein is red, and its absorption spectrum suggests that it binds iron ions, possibly via the predicted zinc finger domain (PubMed:19620981). In contrast, the ortholog from Sulfolobus clearly binds zinc ions via its zinc finger domain, as shown by X-ray crystallography.