Characterization of novel mutations in the catalytic domain of the PCSK9 gene.

OBJECTIVES: To expand our understanding of the structure and function of proprotein convertase subtilisin/kexin type 9 (PCSK9) by studying how naturally occurring mutations in PCSK9 disrupt the function of PCSK9. DESIGN: Mutations in PCSK9 were identified by sequencing of DNA from subjects with hypo- or hypercholesterolemia. The effect of the identified mutations on the autocatalytic cleavage and secretion of PCSK9, as well as the effect on PCSK9-mediated degradation of the low density lipoprotein receptors, were determined in HepG2 or HEK293 cells transiently transfected with mutant PCSK9-containing plasmids. The findings were collated to the clinical characteristics of the subjects possessing these mutations, and the phenotypic effects were analysed in terms of available structural data for PCSK9. RESULTS: Five novel mutations in PCSK9 were identified. Mutation R215H was a gain-of-function mutation which causes hypercholesterolemia. Mutation G236S and N354I were loss-of-function mutations due to failure to exit the endoplasmic reticulum or failure to undergo autocatalytic cleavage, respectively. Mutations A245T and R272Q were most likely normal genetic variants. By comparing the number of patients with gain-of-function mutations in PCSK9 with the number of familial hypercholesterolemia heterozygotes among subjects with hypercholesterolemia, the prevalence of subjects with gain-of-function mutations in PCSK9 in Norway can be estimated to one in 15,000. CONCLUSION: This study has provided novel information about the structural requirements for the normal function of PCSK9. However, more studies are needed to determine the mechanisms by which gain-of-function mutations in PCSK9 cause hypercholesterolemia.

Fully relativistic coupled cluster treatment for parity-violating energy differences in molecules.

Fully relativistic four-component many-body perturbation and coupled cluster electronic structure calculations including electroweak neutral current corrections are presented for a study of parity-violating effects in chiral molecules. For the chiral molecules H2O2 and H2S2, it is demonstrated that electron correlation contributions to the parity-violating energy shifts are small but critically dependent on the molecular geometry.

D- or L-alanine: that is the question.

The question is reopened, whether L- or D-alanine is more stable. Calculated parity-violating energy shifts for the 13 stable conformers of gaseous alanine (the picture shows the global minima) indicate that the stabilization of a certain enantiomer is strongly dependent on its conformation. Naturally occurring L-alanine is preferred for only seven of the investigated structures, which allows no definite conclusion on the relative stability of the two chiral forms to explain the origin of homochirality in living organisms.