This entry represents a subdomain found in the C-terminal cysteine/histidine-rich domain (CRD) of PCSK9 (also known as neural apoptosis-regulated convertase, NARC-1) [1]. PCSK9 has been shown to regulate circulating LDL-R levels by controlling LDL-R degradation. Furthermore, numerous mutations in the PCSK9 gene have been identified and associated with hypercholesterolemia (gain of function) or hypocholesterolemia (loss of function) [2]. The fully folded CRD, shows structural similarity to the resistin homotrimer, a small cytokine associated with obesity and diabetes. The C-terminal domain from PCSK9 consists of three, three-stranded beta-subdomains arranged in a pseudothreefold, and each of the subdomains in the CRD of PCSK9 consists of three structurally conserved disulfide bonds [1].

1: The self-inhibited structure of full-length PCSK9 at 1.9 A reveals structural homology with resistin within the C-terminal domain. Hampton EN, Knuth MW, Li J, Harris JL, Lesley SA, Spraggon G; Proc Natl Acad Sci U S A. 2007;104:14604-14609. PMID:17804797

2: Design and synthesis of truncated EGF-A peptides that restore LDL-R recycling in the presence of PCSK9 in vitro. Schroeder CI, Swedberg JE, Withka JM, Rosengren KJ, Akcan M, Clayton DJ, Daly NL, Cheneval O, Borzilleri KA, Griffor M, Stock I, Colless B, Walsh P, Sunderland P, Reyes A, Dullea R, Ammirati M, Liu S, McClure KF, Tu M, Bhattacharya SK, Liras S, Price DA, Craik DJ; Chem Biol. 2014;21:284-294. PMID:24440079

3: Structural and biophysical studies of PCSK9 and its mutants linked to familial hypercholesterolemia. Cunningham D, Danley DE, Geoghegan KF, Griffor MC, Hawkins JL, Subashi TA, Varghese AH, Ammirati MJ, Culp JS, Hoth LR, Mansour MN, McGrath KM, Seddon AP, Shenolikar S, Stutzman-Engwall KJ, Warren LC, Xia D, Qiu X; Nat Struct Mol Biol. 2007;14:413-419. PMID:17435765

4: The crystal structure of PCSK9: a regulator of plasma LDL-cholesterol. Piper DE, Jackson S, Liu Q, Romanow WG, Shetterly S, Thibault ST, Shan B, Walker NP; Structure. 2007;15:545-552. PMID:17502100

5: Molecular basis for LDL receptor recognition by PCSK9. Kwon HJ, Lagace TA, McNutt MC, Horton JD, Deisenhofer J; Proc Natl Acad Sci U S A. 2008;105:1820-1825. PMID:18250299

6: Antagonism of secreted PCSK9 increases low density lipoprotein receptor expression in HepG2 cells. McNutt MC, Kwon HJ, Chen C, Chen JR, Horton JD, Lagace TA; J Biol Chem. 2009;284:10561-10570. PMID:19224862

7: A proprotein convertase subtilisin/kexin type 9 neutralizing antibody reduces serum cholesterol in mice and nonhuman primates. Chan JC, Piper DE, Cao Q, Liu D, King C, Wang W, Tang J, Liu Q, Higbee J, Xia Z, Di Y, Shetterly S, Arimura Z, Salomonis H, Romanow WG, Thibault ST, Zhang R, Cao P, Yang XP, Yu T, Lu M, Retter MW, Kwon G, Henne K, Pan O, Tsai MM, Fuchslocher B, Yang E, Zhou L, Lee KJ, Daris M, Sheng J, Wang Y, Shen WD, Yeh WC, Emery M, Walker NP, Shan B, Schwarz M, Jackson SM; Proc Natl Acad Sci U S A. 2009;106:9820-9825. PMID:19443683

8: Proprotein convertase substilisin/kexin type 9 antagonism reduces low-density lipoprotein cholesterol in statin-treated hypercholesterolemic nonhuman primates. Liang H, Chaparro-Riggers J, Strop P, Geng T, Sutton JE, Tsai D, Bai L, Abdiche Y, Dilley J, Yu J, Wu S, Chin SM, Lee NA, Rossi A, Lin JC, Rajpal A, Pons J, Shelton DL; J Pharmacol Exp Ther. 2012;340:228-236. PMID:22019884

9: An antibody against the C-terminal domain of PCSK9 lowers LDL cholesterol levels in vivo. Schiele F, Park J, Redemann N, Luippold G, Nar H; J Mol Biol. 2014;426:843-852. PMID:24252255