The trypanosomatid parasite Trypanosoma brucei synthesizes fatty acids in the mitochondrion using the type II fatty acid synthesis (FAS) machinery. When mitochondrial FAS was characterized in T. brucei, all of the enzymatic components were identified based on their homology to yeast mitochondrial FAS enzymes, except for 3-hydroxyacyl-ACP dehydratase. Here we describe the characterization of T. brucei mitochondrial 3-hydroxyacyl-ACP dehydratase (TbHTD2), which was identified by its similarity to the human mitochondrial dehydratase. TbHTD2 can rescue the respiratory deficient phenotype of the yeast knock-out strain and restore the lipoic acid content, is localized in the mitochondrion and exhibits hydratase 2 activity.
Processing and metabolism of beta-amyloid precursor protein (APP) and generation of a variety of beta-amyloid (Abeta) peptides in the human brain is essentially associated with pathophysiology of Alzheimer's disease (AD). APP degradation activity of the 68 kDa serine protease, which was originally prepared from familial AD lymphoblastoid cells and harbors beta-secretase-like activity, was analyzed by Western blot using anti Abeta 1/40 antibody and anti APP cytoplasmic domain (CT) antibody. Native lymphocyte APP (LAPP) prepared from normal or AD-derived lymphoblastoid cells was degraded by the protease, generating a 16 kDa Abeta-bearing C-terminal fragment of APP. N-terminal amino acid sequencing of the fragment indicated that the protease cleaves LAPP at the Abeta-N-terminus. When the LAPP was treated with chondroitinase ABC prior to proteolysis, the activity to generate the fragment was inhibited, but pretreatment with heparitinase resulted in no effect. Native hippocampal APP prepared from normal brain, however, did not generate the 16 kDa peptide by the protease treatment. These results suggest that the process of APP degradation and Abeta-peptides generation, including beta-secretase activity, is associated with tissue specificity of both APP substrate and proteases. They also indicate that sulfated glycoconjugates attached to a portion of APP isoforms may play a role as a molecular determinant in the proteolysis.
Type IV collagenase (gelatinase) is a 70,000 dalton neutral metalloproteinase that specifically cleaves type IV collagen in addition to degrading denatured collagen (gelatin). It is secreted in a latent proenzyme form that is converted proteolytically in the extracellular space to a 62,000 dalton active enzyme. The primary structure, enzymatic properties as well as gene structure, demonstrate that type IV collagenase is closely related with the other well characterized metalloproteinases, interstitial collagenase and stromelysin. However, the structure of type IV collagenase differs from the others in that it is larger and contains three internal repeats that resemble the type II domains of fibronectin. Also, initial characterization of the promoter region of the gene indicates that its regulation differs from the other proteinase genes. Type IV collagenase is presumably required for the normal turnover of basement membranes. Augmented activity is linked with the invasive potential of tumor cells and the enzyme is believed to play a major role in the penetration of basement membranes by metastatic cells. Measurements of enzyme activity and mRNA levels as well as immunostaining of a variety of tumor cells and tissues suggest that assays for the enzyme may have value in the follow-up of malignant growth.
Commercial inactivated parenteral influenza vaccines reduced febrile (> or = 38 degrees C) respiratory illness by 53% (95% CL: 41-63%) during a 3 week outbreak in 1998 when A/Sydney/5/97(H3N2)-like influenza viruses were shown to be the predominant etiological agents and an older antigenic variant, A/Nanchang/933/95, served as the vaccine virus. The calculatory efficacy for preventing virologically diagnosed influenza infections was 57% (95% CL: 40-68%). The study population consisted of 1374 young male military conscripts. Vaccination coverage on a voluntary basis was 67%. Vaccination was ineffective in preventing febrile illness during a second epidemic wave lasting 2 weeks when mainly adenoviruses were shown to have been circulating in the garrison. Out of the 36 nasopharyngeal aspirates positive for influenza A by antigen detection, 18 A/Sydney/5/97-like strains (10 from non-vaccinated and eight from vaccinated subjects) and two A/Nanchang/933/95-like strains (both from non-vaccinated subjects) were isolated in MDCK cell cultures. Intraepidemic variation was detected among the A/Sydney/5/97-like field strains in their HA1 sequences and reactivity in HI tests, but no evidence was obtained that this variation would have been of significance to the virus in breaking through the vaccination-induced immunity.
This study examined whether the Trp64Arg mutation in the beta3-adrenergic receptor (beta3AR) and the A-->G mutation in the uncoupling protein-1 (UCP-1) genes have associations with weight loss and subsequent weight maintenance. Seventy-seven obese (body mass index range, 29-46 kg/m2), clinically healthy, premenopausal women were studied. A 12-wk weight reduction by very low calorie diet (VLCD) was followed by a 40-wk weight maintenance phase. The subjects were divided into four groups according to their beta3AR and UCP-1 genotype: no mutation (control; n=37), only Trp64Arg mutation in the beta3AR gene (n=12), only A-->G mutation in the UCP-1 gene (n=23), and both mutations (n=5). Subjects with both mutations had a lower weight reduction during VLCD than the controls [-10.5+/-0.6 (+/-SEM) vs. -14.0+/-0.5 kg; P=0.051, by ANOVA]. During the maintenance phase, weight in subjects with both mutations increased by 5.8+/-1.5 kg, but remained unchanged in the controls (-0.5+/-0.8 kg; P=0.041). The changes in weight in subjects with only one of the mutation were close to the results in the controls. Resting energy expenditure, adjusted for fat mass, fat-free mass, and maximal aerobic power, did not change differently between the groups throughout the study. The results suggest that a combination of the Trp64Arg mutation in the beta3AR and the A-->G mutation in the UCP-1 genes may be associated with faster weight gain after a VLCD.
X-linked adrenoleukodystrophy is a peroxisomial disorder caused by mutations in the ABCD1 gene. Adrenomyeloneuropathy is the second most frequent phenotype (25-46%) of this disease and classically presents in adulthood with spastic paraparesis. Female heterozygotes can be symptomatic, but they are frequently misdiagnosed as having multiple sclerosis.
We report a novel missense mutation in the ABCD1 gene in a 47-year-old French-Canadian female with spastic paraparesis and no confirmed family history of X-linked adrenoleukodystrophy. The mutation is located on exon 1 and causes the amino acid substitution of a valine for an alanine in a region of the protein highly conserved between mouse and man.
Adrenomyeloneuropathy must be considered in the differential diagnosis of spastic paraparesis in men or women. This is an initial report of an ABCD1 gene mutation in the French-Canadian population, which should lead to the recognition of other cases in the future.
Five point mutations within the amyloid beta-protein (Abeta) sequence of the APP gene are associated with hereditary diseases which are similar or identical to Alzheimer's disease and encode: the A21G (Flemish), E22G (Arctic), E22K (Italian), E22Q (Dutch) and the D23N (Iowa) amino acid substitutions. Although a substantial body of data exists on the effects of these mutations on Abeta production, whether or not intra-Abeta mutations alter degradation and how this relates to their aggregation state remain unclear. Here we report that the E22G, E22Q and the D23N substitutions significantly increase fibril nucleation and extension, whereas the E22K substitution exhibits only an increased rate of extension and the A21G substitution actually causes a decrease in the extension rate. These substantial differences in aggregation together with our observation that aggregated wild type Abeta(1-40) was much less well degraded than monomeric wild type Abeta(1-40), prompted us to assess whether or not disease-associated intra-Abeta mutations alter proteolysis independent of their effects on aggregation. Neprilysin (NEP), insulin degrading enzyme (IDE) and plasmin play a major role in Abeta catabolism, therefore we compared the ability of these enzymes to degrade wild type and mutant monomeric Abeta peptides. Experiments investigating proteolysis revealed that all monomeric peptides are degraded similarly by IDE and plasmin, but that the Flemish peptide was degraded significantly more slowly by NEP than wild type Abeta or any of the other mutant peptides. This finding suggests that resistance to NEP-mediated proteolysis may underlie the pathogenicity associated with the A21G mutation.
The paper is concerned with the results of recent researches devoted to studies of the structure, properties and physiological role of alpha 2-macroglobulin, one of main inhibitors of blood proteolytic enzymes. Data are presented on its primary and quaternary structure, mechanisms of interaction with proteinases. The role of alpha 2-macroglobulin in regulation of the activity of proteinases participating in blood coagulation, fibrinolysis, kininogenesis, immune reactions is shown. Possibilities of its application in medicine are discussed.
Alpha-methylacyl-CoA racemase (Amacr) catalyzes the racemization of alpha-methyl-branched CoA esters. Sequence comparisons have shown that this enzyme is a member of the family III CoA transferases. The mammalian Amacr is involved in bile acid synthesis and branched-chain fatty acid degradation. In human, mutated variants of Amacr have been shown to be associated with disease states. Amino acid sequence alignment of Amacrs and its homologues from various species revealed 26 conserved protic residues, assumed to be potential candidates as catalytic residues. Amacr from Mycobacterium tuberculosis (MCR) was taken as a representative of the racemases. To determine their importance for efficient catalysis, each of these 26 protic residues of MCR was mutated into an alanine, respectively, and the mutated variants were overexpressed in Escherichia coli. It was found that four variants (R91A, H126A, D156A, and E241A) were properly folded but had much decreased catalytic efficiency. Apparently, Arg91, His126, Asp156, and Glu241 are important catalytic residues of MCR. The importance of these residues for catalysis can be rationalized by the 1.8 A resolution crystal structure of MCR, which shows that the catalytic site is at the interface between the large and small domain of two different subunits of the dimeric enzyme. This crystal structure is the first structure of a complete enzyme of the bile acid synthesis pathway. It shows that MCR has unique structural features, not seen in the structures of the sequence related formyl-CoA transferases, suggesting that the family III CoA transferases can be subdivided in at least two classes, being racemases and CoA transferases.
In this study we have constructed a number of plants (cybrids), in which the nuclear genome of Nicotiana plumbaginifolia is combined with the plastome of Atropa belladonna, or the nuclear genome of N. tabacum with plastomes of Lycium barbarum, Scopolia carniolica, Physochlaine officinalis or Nolana paradoxa. Our biochemical and immunological analyses prove that in these cybrids the biogenesis of the chlorophyll a/b binding proteins (CAB) of the light harvesting complex II (LHCII) is altered. Besides normal sized CAB polypeptides of 27, 25.5 and 25 kDa, which become less abundant, the cybrids analyzed have additional polypeptides of 26, 24.5 and 24 kDa. Direct protein micro-sequencing showed that at least two truncated 26 kDa CAB polypeptides in plant cells containing a nucleus of N. plumbaginifolia and plastids of A. belladonna are encoded by the type 1 Lhcb genes. These polypeptides are 11-12 amino acids shorter at the N-terminus than the expected size. Based on the available data we conclude that the biogenesis of the LHCII in vivo may depend on plastome-encoded factor(s). These results suggest that plastome-encoded factors that cause specific protein degradation and/or abnormal processing might determine compartmental genetic incompatibility in plants.