Conformation-gated binding underlies kinetic asymmetry and negative cooperativity in ATP:cob(I)alamin adenosyltransferase.

ABSTRACT: Vitamin B₁₂ (cobalamin) is a high-value yet scarce cofactor critical for metabolic homeostasis, necessitating efficient handling mechanisms. ATP:cob(I)alamin adenosyltransferase (MMAB) plays a central role in synthesizing, delivering, and repairing 5'-deoxyadenosylcobalamin (AdoCbl), but the kinetic mechanisms regulating this process, including negative cooperativity, remain unclear. Using single-molecule relative fluorescence spectroscopy, we reveal that conformation-gated binding mechanism, involving a required structural rearrangement prior to the first cofactor association, dictates MMAB's interaction kinetics. This mechanism slows the association of a second AdoCbl, resulting in strong negative cooperativity, favoring the singly bound state, and optimizing AdoCbl handling.

SUBMITTER: Yan G 

PROVIDER: S-EPMC12431680 | biostudies-literature | 2025 Aug

REPOSITORIES: biostudies-literature