Background-Accumulation and oxidation of LDL are believed to be important initiating factors in atherosclerosis.Oxidized LDL is recognized by the immune system, and animal studies have suggested that these immune responses have a protective effect against atherosclerosis. Aldehyde-modified peptide sequences in apolipoprotein B-100 (apoB-100) are major targets for these immune responses. Methods and Results-Human IgG1 antibodies against 2 malondialdehyde (MDA)-modified apoB-100 peptide sequences were produced through screening of a single-chain antibody-fragment library and subsequent cloning into a pcDNA3 vector. Three weekly doses of these antibodies were injected into male apoE Ϫ/Ϫ mice. Phosphate-buffered saline and human IgG1 antibodies against fluorescein isothiocyanate were used as controls. One of the IgG1 antibodies significantly and dose-dependently reduced the extent of atherosclerosis as well as the plaque content of oxidized LDL epitopes and macrophages. In cell culture studies, human monocytes were incubated with native LDL or oxidized LDL, in the presence of antibodies. The same antibody induced an increase in monocyte binding and uptake of oxidized LDL. Conclusions-These findings suggest that antibodies are important mediators of atheroprotective immune responses directed to oxidized LDL. Thus, passive immunization against MDA-modified apoB-100 peptide sequences may represent a novel therapeutic approach for prevention and treatment of cardiovascular disease.
Cytochromes of c‐type contain covalently bound haem and in bacteria are located on the periplasmic side of the cytoplasmic membrane. More than eight different gene products have been identified as being specifically required for the synthesis of cytochromes c in Gram‐negative bacteria. Corresponding genes are not found in the genome sequences of Gram‐positive bacteria. Using two random mutagenesis approaches, we have searched for cytochrome c biogenesis genes in the Gram‐positive bacterium Bacillus subtilis. Three genes, resB, resC and ccdA, were identified. CcdA has been found previously and is required for a late step in cytochrome c synthesis and also plays a role in spore synthesis. No function has previously been assigned for ResB and ResC but these predicted membrane proteins show sequence similarity to proteins required for cytochrome c synthesis in chloroplasts. Attempts to inactivate resB and resC in B. subtilis have indicated that these genes are essential for growth. We demonstrate that various nonsense mutations in resB or resC can block synthesis of cytochromes c with no effect on other types of cytochromes and little effect on sporulation and growth. The results strongly support the recent proposal that Gram‐positive bacteria, cyanobacteria, ε‐proteobacteria, and chloroplasts have a similar type of machinery for cytochrome c synthesis (System II), which is very different from those of most Gram‐negative bacteria (System I) and mitochondria (System III).
We demonstrate that the cccB gene, identified in the Bacillus subtilis genome sequence project, is the structural gene for a 10-kDa membrane-bound cytochrome
The Gram-positive bacterium Bacillus subtilis contains two respiratory oxidases of the haem-copper superfamily: cytochrome aa 3, which is a quinol oxidase, and cytochrome caa 3, which is a cytochrome c oxidase. Cytochrome c oxidase uniquely contains a di-copper centre, CuA. B. subtilis CtaG is a membrane protein encoded by the same gene cluster as that which encodes the subunits of cytochrome c oxidase. The role of B. subtilis CtaG and orthologous proteins present in many other Gram-positive bacteria has remained unexplored. The sequence of CtaG is unrelated to that of CtaG/Cox11p of proteobacteria and eukaryotic cells. This study shows that B. subtilis CtaG is essential for the formation of active cytochrome caa 3 but is not required for assembly of the core subunits I and II with haem in the membrane and it has no role in the synthesis of active cytochrome aa 3. B. subtilis YpmQ, a homologue to Sco1p of eukaryotic cells, is also a membrane-bound cytochrome c oxidase-specific assembly factor. Properties of CtaG- and YpmQ-deficient mutants were compared. Cells lacking YpmQ showed a low cytochrome c oxidase activity and this defect was suppressed by the supplementation of the growth medium with copper ions. It has previously been proposed that YpmQ/Sco1p is involved in synthesis of the CuA centre. The results of this study are consistent with this proposal but the exact role of YpmQ in assembly of cytochrome c oxidase remains to be elucidated.
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