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21.
Regularly arrayed surface (glyco)proteins—often referred to as S layers—are a common feature of the cell envelopes of almost all archaebacteria. We have selected some examples (Halobacterium, Sulfolobus, Thermoproteus, Pyrobaculum, Staphylothermus), and we describe the structure of their surface layers as revealed primarily by electron crystallography. In spite of a considerable diversity in shapes and dimensions, some common structural features emerge from the comparison. The glycoprotein arrays are composed of oligomeric units which are anchored in the plasma membrane; extended spacer or linker domains maintain the bulk of the more or less porous surface layers at a constant distance above the membrane surface, thus creating a quasi-periplasmic compartment. Functions ascribed to surface layers, such as compartmentalization, shape maintenance and determination, and adhesion are discussed. 相似文献
22.
Isolation and characterization of the human hepatic lipase gene 总被引:7,自引:0,他引:7
D Ameis G Stahnke J Kobayashi J McLean G Lee M Büscher M C Schotz H Will 《The Journal of biological chemistry》1990,265(12):6552-6555
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Coexistence of abnormalities of hepatic lipase and lipoprotein lipase in a large family. 总被引:5,自引:0,他引:5
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J H Auwerx S P Babirak J E Hokanson G Stahnke H Will S S Deeb J D Brunzell 《American journal of human genetics》1990,46(3):470-477
A large family is reported with familial hepatic triglyceride lipase (HTGL) deficiency and with the coexistence of reduced lipoprotein lipase (LPL) similar to the heterozygote state of LPL deficiency. The proband was initially detected because of hypertriglyceridemia and chylomicronemia. He was later demonstrated to have beta-VLDL despite an apo E3/E3 phenotype and the lack of stigmata of type III hyperlipoproteinemia. The proband had no HTGL activity in postheparin plasma. Two of his half-sisters had very low HTGL activity (39 and 31 nmol free fatty acids/min/ml; normal adult female greater than 44). His son and daughters had decreased HTGL activity (normal male and preadolescent female greater than 102), which would be expected in obligate heterozygotes for HTGL deficiency. Low HTGL activity was associated with LDL particles which were larger and more buoyant. Several family members, including the proband, had reduced LPL activity and mass less than that circumscribed by the 95% confidence-interval ellipse for normal subjects and had hyperlipidemia similar to that described in heterozygote relatives of patients with LPL deficiency. All the sibs with hyperlipidemia had a reduced LPL activity and mass, while subjects with isolated reduced HTGL (with normal LPL activity) had normal lipid phenotypes. Analysis of genomic DNA from these subjects by restriction-enzyme digestion revealed no major abnormalities in the structure of either the HTGL or the LPL gene. Compound heterozygotes for HTGL and LPL deficiency show lipoprotein physiological characteristics typical for HTGL deficiency, while their variable lipid phenotype is typical for LPL deficiency. 相似文献
25.
Summary Hagfish hemoglobin has three main components, one of which is Hb III. It is monomeric and consists of 148 amino acid residues (M = 17 350). Its complete primary structure, previously published, is discussed here. The proximal amino acid (F8) of the heme linkage is histidine as always in the hemoglobins, but the regularly expected distal histidine E7 is substituted by glutamine. This substitution, leading to a new kind of heme linkage, has hitherto only been demonstrated in opossum hemoglobin. It is suggested that E7, Gln, is directed out of the heme pocket, and that the adjacent Ell, Ile, is directed toward the inside of the pocket, giving the distal heme contact instead of histidine.Myxine Hb III has an additional tail of 9 amino acid residues at its N-terminal end, as has the hemoglobin ofLampetra fluviatilis. The genetic codes ofMyxine andLampetra hemoglobins show 117 differences, in spite of many morphological resemblances between hagfish and lamprey. Their primary hemoglobin structures show differences substantial enough to bo compatible with the divergence of the two families some 400–500 million years ago. 相似文献
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Human hepatic triglyceride lipase: cDNA cloning, amino acid sequence and expression in a cultured cell line 总被引:5,自引:0,他引:5
Gisela Stahnke Rolf Sprengel Jan Augustin Hans Will 《Differentiation; research in biological diversity》1987,35(1):45-52
By immunoscreening of a human cDNA expression library and hybridization of colonies, four partially overlapping cDNA clones of human hepatic triglyceride lipase (HTGL) mRNA were isolated. The clones included the complete coding sequence, the 3'- and at least part of the 5'-untranslated region. The length of the composite HTGL cDNA segment (1.7 kb) was consistent with the size of the mRNA identified in an established human hepatoma cell line. DNA-sequence analysis of cDNAs of partially unspliced mRNAs, and of cloned genomic DNA indicated that the HTGL coding sequence comprises at least six exons. As predicted from the cDNA, the unprocessed HTGL protein has a molecular weight of 56, three potential glycosylation sites, and a signal peptide of 23 amino acids. Sequence comparison with cDNA of other lipases, including rat hepatic lipase, revealed 30%-75% protein-sequence homology. The data establish that HTGL is a secretory protein produced in the hepatocyte, and that its synthesis can be continued in permanent cell lines of hepatoma origin. Our studies also showed that HTGL is another member of a lipase gene family which has interfacial binding sites and possibly other functional domains in common. 相似文献
29.
Floral microcharacters of the genus Chrysolaena H. Rob. (Vernonieae, Asteraceae) were analysed in detail for the first time in order to evaluate the taxonomic position of conflictive species in the group. The results were also compared with studies carried out in species of related genera. In addition to distinctive microcharacters previously studied in some species of the genus, other characters such as trichome types of the corolla, style, anthers and cypselae have been analysed for the first time. The presence of glandular apical appendage and cypselae are common characteristics among species Chrysolaena. In addition to these, this study shows that presence of glands on the style and corollas is another consistent characteristic in the genus. However, the absence of basal stylar node would not be a diagnostic character since this varies widely among species. The results indicate that most of the microcharacters of Chrysolaena analysed are quite consistent in the genus, but they are no more consistent than the pollen morphology (type 'C') and chromosome base number (x = 10). Until now, these last two features would be most useful for separating Chrysolaena from the related genera Lessingianthus and Lepidaploa. At species level, the results show that related species can be distinguished by the different combinations of floral microcharacters. The value of microcharacters could be increased if they are combined with other morphological, cytological, and palynological data. 相似文献
30.
Pla M La Paz JL Peñas G García N Palaudelmàs M Esteve T Messeguer J Melé E 《Transgenic research》2006,15(2):219-228
Maize is one of the main crops worldwide and an increasing number of genetically modified (GM) maize varieties are cultivated
and commercialized in many countries in parallel to conventional crops. Given the labeling rules established e.g. in the European
Union and the necessary coexistence between GM and non-GM crops, it is important to determine the extent of pollen dissemination
from transgenic maize to other cultivars under field conditions. The most widely used methods for quantitative detection of
GMO are based on real-time PCR, which implies the results are expressed in genome percentages (in contrast to seed or grain
percentages). Our objective was to assess the accuracy of real-time PCR based assays to accurately quantify the contents of
transgenic grains in non-GM fields in comparison with the real cross-fertilization rate as determined by phenotypical analysis.
We performed this study in a region where both GM and conventional maize are normally cultivated and used the predominant
transgenic maize Mon810 in combination with a conventional maize variety which displays the characteristic of white grains
(therefore allowing cross-pollination quantification as percentage of yellow grains). Our results indicated an excellent correlation
between real-time PCR results and number of cross-fertilized grains at Mon810 levels of 0.1–10%. In contrast, Mon810 percentage
estimated by weight of grains produced less accurate results. Finally, we present and discuss the pattern of pollen-mediated
gene flow from GM to conventional maize in an example case under field conditions. 相似文献