The folding pathway of prothrombin

Prothrombin is a coagulation factor composed of γ-carboxyglutamate, kringle 1, kringle 2, and protease domains. An extensive set of interactions links the N-terminal γ-carboxyglutamate domain to kringle 1, and the C-terminal protease domain to kringle 2. These 2 halves of the multidomain structure interact via the collapse of kringle 1 on the protease domain, thereby defining the physiologically predominant closed conformation.

To investigate how the spatial arrangements of constitutive domains and interdomain contacts are formed during folding.

The chemical denaturation pathway of prothrombin was studied using single-molecule and ensemble spectroscopic techniques.

Under strongly denaturing conditions, the four domains of prothrombin separate, and the protein becomes elongated. As folding progresses from this unfolded, elongated state, prothrombin acquires secondary and tertiary structural elements and organizes the hydrophobic residues into its core, thereby promoting domain folding. Subsequently, an extensive set of interdomain contacts organize the arrangement observed in the native state.

Proper domain folding is necessary for the formation of interdomain contacts that stabilize the closed form of prothrombin. The results are relevant in light of recent findings implicating prothrombin conformations with destabilized interdomain contacts in the onset of certain coagulopathies.