A consensus sequence (~90 aa) that includes six cysteines which form disulphide bonds; it can be drawn as apple-shaped. Found as a fourfold repeat in plasma kallikrein and coagulation factor XI, both serine peptidases. Mutations in apple 4 cause factor XI deficiency, an inherited bleeding disorder.
http://smart.embl-heidelberg.de/smart/do_annotation.pl?DOMAIN=APPLE&BLAST=DUMMY Image of the structure.
Subjects: Chemistry — Medicine and Health.