Crystal structure of L68V mutant of human cystatin C
[CYTC_HUMAN] Defects in CST3 are the cause of amyloidosis type 6 (AMYL6) [MIM:105150]; also known as hereditary cerebral hemorrhage with amyloidosis (HCHWA), cerebral amyloid angiopathy (CAA) or cerebroarterial amyloidosis Icelandic type. AMYL6 is a hereditary generalized amyloidosis due to cystatin C amyloid deposition. Cystatin C amyloid accumulates in the walls of arteries, arterioles, and sometimes capillaries and veins of the brain, and in various organs including lymphoid tissue, spleen, salivary glands, and seminal vesicles. Amyloid deposition in the cerebral vessels results in cerebral amyloid angiopathy, cerebral hemorrhage and premature stroke. Cystatin C levels in the cerebrospinal fluid are abnormally low.  Genetic variations in CST3 are associated with age-related macular degeneration type 11 (ARMD11) [MIM:611953]. ARMD is a multifactorial eye disease and the most common cause of irreversible vision loss in the developed world. In most patients, the disease is manifest as ophthalmoscopically visible yellowish accumulations of protein and lipid that lie beneath the retinal pigment epithelium and within an elastin-containing structure known as Bruch membrane.
[CYTC_HUMAN] As an inhibitor of cysteine proteinases, this protein is thought to serve an important physiological role as a local regulator of this enzyme activity.
Publication Abstract from PubMed
Wild-type human cystatin C (hCC wt) is a low-molecular-mass protein (120 amino-acid residues, 13 343 Da) that is found in all nucleated cells. Physiologically, it functions as a potent regulator of cysteine protease activity. While the biologically active hCC wt is a monomeric protein, all crystallization efforts to date have resulted in a three-dimensional domain-swapped dimeric structure. In the recently published structure of a mutated hCC, the monomeric fold was preserved by a stabilization of the conformationally constrained loop L1 caused by a single amino-acid substitution: Val57Asn. Additional hCC mutants were obtained in order to elucidate the relationship between the stability of the L1 loop and the propensity of human cystatin C to dimerize. In one mutant Val57 was substituted by an aspartic acid residue, which is favoured in beta-turns, and in the second mutant proline, a residue known for broadening turns, was substituted for the same Val57. Here, 2.26 and 3.0 A resolution crystal structures of the V57D andV57P mutants of hCC are reported and their dimeric architecture is discussed in terms of the stabilization and destabilization effects of the introduced mutations.
Structural characterization of V57D and V57P mutants of human cystatin C, an amyloidogenic protein.,Orlikowska M, Szymanska A, Borek D, Otwinowski Z, Skowron P, Jankowska E Acta Crystallogr D Biol Crystallogr. 2013 Apr;69(Pt 4):577-86. doi:, 10.1107/S0907444912051657. Epub 2013 Mar 14. PMID:23519666
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.