NTR/C345C domain, complement C5 subfamily; The NTR domain found in complement C5 is also known as C345C because it occurs at the C-terminus of complement C3, C4 and C5. Complement C5 is activated by C5 convertase, which itself is a complex between C3b and C3 convertase. The small cleavage fragment, C5a, is the most important small peptide mediator of inflammation, and the larger active fragment, C5b, initiates late events of complement activation. The NTR/C345C domain is important in the function of C5 as it interacts with enzymes that convert C5 to the active form, C5b. The domain has also been found to bind to complement components C6 and C7, and may specifically interact with their factor I modules.
Jiyao W et al.(2023). "The conserved domain database in 2023.",