首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 31 毫秒
1.
    
-Crystallin is the major and most abundant lens protein present in the eye lens of lower vertebrates such as amphibian and piscine species. To facilitate structural characterization of-crystallins isolated from the lens of the bullfrog (Rana catesbeiana), a cDNA mixture was synthesized from the poly(A)+mRNA isolated from fresh eye lenses. cDNA encoding-crystallin was then amplified using polymerase chain reaction (PCR) based on two primers designed according to the relatively conserved N- and C-terminal sequences of known-crystallins from teleostean fishes. PCR-amplified product corresponding to-crystallin isoforms was obtained, which was then subcloned in pUC18 vector and transformed intoEscherichia coli strain JM109. Plasmids containing amplified-crystallin cDNAs were purified and prepared for nucleotide sequencing by the dideoxynucleotide chain-termination method. Sequencing several clones containing DNA inserts of about 0.54 kb revealed the presence of two isoforms with an open reading frame of 534 base pairs, covering two-crystallins each with a deduced protein sequence of 177 amino acids including the translation-initiating methionine. These-crystallins of pI 6.364 and 6.366 contain a low-methionine content of 2.81%, in contrast to 11–16% obtained for those-crystallins with high-methionine content from most teleostean lenses. Pairwise sequence comparison of bullfrog-crystallins with those published sequences of-crystallins from carp, shark,Xenopus and anotherRana frog, bovine, and human lenses indicates that there is only 46–63% sequence similarity among these species, revealing that amphibians possess a very complex and heterogeneous group of-crystallins even from closely related species ofRana frogs. The sequence analysis and comparison of various isoforms of the frog-crystallin family provide a firm basis for identifying these lens proteins as members of a multigene family more complex than that reported for mammalian-crystallins.  相似文献   

2.
Two new asterosaponins, (20R)-3-O--D-(2-O-methylxylopyranosyl)-24-propylcholest-4-ene-3,6,8,15,16,29-hexaol (sanguinoside A) and (20R,24S)-3-O--D-(2,3,4-tri-O-methylxylopyranosyl)-5-cholestane-3,4,6,8,15,24-hexaol (sanguinoside B), were isolated from two species of Pacific Far Eastern Starfish Henricia sanguinolenta and H. leviuscula leviuscula, collected in the Sea of Okhotsk. Both glycosides contain aglycones with pentahydroxysteroid nuclei of similar structures, which are substituted at the 3-hydroxy group with differently methylated -D-xylosyl residues. Sanguinoside A has an unusual structure of its aglycone side chain, whereas sanguinoside B has a unique permethylated carbohydrate chain. In addition, laevisculoside G, a known glycoside, was identified in the H. leviuscula starfish. The structures of the isolated glycosides were established by interpreting their spectral data and by comparing their spectral characteristics with those of known compounds.  相似文献   

3.
The stable isotope ratios of nitrogen were measured in the mysid,Neomysis intermedia, together with various biogenic materials in a eutrophic lake, Lake Kasumigaura, in Japan throughout a year of 1984/85. The mysid, particulate organic matter (POM, mostly phytoplankton), and zooplankton showed a clear seasonal change in 15N with high values in spring and fall, but the surface bottom mud did not. A year to year variation as well as seasonal change in 15N was found in the mysid. The annual averages of 15N of each material collected in 1984/85 are as follows: surface bottom mud, 6.3 (range: 5.7–6.9); POM, 7.9 (5.8–11.8); large sized mysid, 11.6 (7.7–14.3); zooplankton, 12.5 (10.0–16.4); prawn, 13.2 (9.9–15.4); goby, 15.1 (13.8–16.7). The degree of15N enrichment by the mysid was determined as 3.2 by the laboratory rearing experiments. The apparent parallel relationship between the POM and the mysid in the temporal patterns of 15N with about 3 difference suggests the POM (mostly phytoplankton) as a possible food source ofN. intermedia in this lake through the year.  相似文献   

4.
Summary The mature labial disc, when implanted into a larva of the same age, undergoes metamorphosis along with the host and produces one lateral half of the medi- and distiproboscis. On the basis of results obtained from transplanted disc halves (including the separate peripodial membrane) a tentative fate map of the labial disc was constructed, which shows most of the presumptive mediproboscis to be located in the dorsal, and most of the presumptive distiproboscis in the ventral part of the disc. The distal protion of the peripodial membrane also contains imaginal anlagen, viz. part of the mediproboscis, prementum, and labellar cap anlagen. The involvement of this part of the peripodial membrane was checked by a careful histological analysis of labial disc development during the first ten hours after prepupation. The results were compared with the situation described forCalliphora imaginal discs.In addition, a detailed morphological analysis was made of the proboscis of the homoeotic mutantproboscipedia (pb). At 27°C,pb changes the distiproboscis into a telopodite (leg segments distal to the coxa); the (unchanged) prementum may therefore correspond to the coxa. At 15° C, the tarsus of this homoeotic telopodite is replaced to a greater or lesser extent by an arista. The present analysis thus confirms (a) the fundamental morphological correspondence of the medi- and distiproboscis with the labium of other insects, and (b) the fundamental developmental correspondence of the labial, antennal, and leg discs.K. K. was a member of the 8th International Research Group in Developmental Biology, and was the recipient of a UNESCO travel grant.)  相似文献   

5.
The effects of fertilization [control (C), 200kgNha–1+25kgP ha–1 (LNP) and 400kgNha–1+ 50kgP ha–1 (HNP)] on fine root dynamics were examined in a 40-year-old Larix leptolepis plantation in central Korea. The average fine root biomass during the growing season for C, LNP and HNP was 957, 934 and 814kgha–1, respectively, whereas the fine root production for C, LNP and HNP was 2103, 2131 and 2066kgha–1, respectively. Nitrogen and P inputs into the soil via fine root turnover for C, LNP and HNP were 23.0 and 1.2, 23.3 and 1.2 and 22.6 and 1.2kgha–1, respectively. There were no significant differences in fine root biomass, production and N and P inputs through fine root turnover between the fertilization treatments during the first growing season after fertilization.  相似文献   

6.
Summary Isoelectric focusing of extracts from the endosperm of mature grains of hexaploid wheat and related species was used to study the genetic control of Iodine binding factor (IBF). Ten IBF bands were present in Chinese Spring (CS) and analysis of the nullisomictetrasomic and ditelosomic lines of CS showed nine of them to be controlled by genes on the long arms of the homoeologous group 5 chromosomes. Five alleles were detected at Ibf-A1 locus, four at Ibf-B1 and four at Ibf-D1 among a sample of 46 wheat genotypes. Homoeoloci were found on chromosome 5R of Secale cereale, 5E of Agropyron elongatum, 5U of Aegilops umbellulata, 5Agi of Agropyron intermedium, 5S1 and 4S1 of Aegilops sharonensis and 4H of Hordeum vulgare.  相似文献   

7.
A new bythitid genus and species, Tuamotuichthys bispinosus, is described from an adult male (88mm SL), caught by dredge in 1990, off Morane Atoll, Tuamotu Archipelago (23°0843 S, 137°0919 W, 536m). It is characterized by having large scales on head and body, two opercular spines, few gill rakers (total 11, 3 of them long), depressed head, vertically expanded posterior maxilla, and a short predorsal (29% SL), each of which resembles several known genera (Calamopteryx, Cataetyx, Diplacanthopoma, Grammonus, and Lucifuga). The combination of character states, however, does not fit any of the known bythitid genera.  相似文献   

8.
We have analyzed the hemoglobins of five individual trout from the Ohrid Lake (Salmo L. typicus) by electrophoretic methods, by reversed-phase high-performance liquid chromatography, and by limited structural analyses. The two major classes of hemoglobin are type I (35% of total) and type IV (65%). Type IV is the major oxygen-transporting hemoglobin; it consists of three types of chain (in about equal quantities) and three types of chain (one major and two minor types). Several structural differences have been observed between these three (IV) chains and between the three (IV) chains, suggesting a complex genetic system governing the synthesis of these proteins. Moreover, a few amino acid substitutions occur at positions involved in contacts between chains, which suggests that differences in oxygen affinity may exist between these various type IV hemoglobins. Type I hemoglobin is less complex because it contains one type of chain and two chains; the latter two differ in numerous positions, suggesting duplications of the (I)-globin gene. The and chains of type I hemoglobin differ considerably from the and chains of type IV hemoglobin, indicating the existence of (I)- and (I)-globin genes separate from the (IV)- and (IV)- globin genes.This study was supported in part by the Yugoslav-American Joint Funds, pp 812 (to G.D.E.), and by United States Public Health Service Research Grant HLB-05168 (to T.H.J.H.).  相似文献   

9.
Summary The DNA base sequences of the entire chimpanzee 1 globin gene and an additional 1 kb of DNA flanking both the human and chimpanzee genes have been determined. Whereas the human 1 gene contains a termination codon in the sixth position, the chimpanzee gene appears to be functional. This finding confirms Proudfoot et al.'s suggestion that the human 1 gene was recently inactivated. Like the corresponding human 1 and 2 genes, the first and second introns of the chimpanzee 1 gene are occupied largely by tandem repeats of short oligonucleotides. These tandem repeats have undergone several rearrangements since the divergence of the human and chimpanzee 1 genes.  相似文献   

10.
    
Summary By using rifampicin to increase the rate of and synthesis in a heterodiploid strain of E. coli carrying the mutation rif pr (Km7), which codes for a rifampicin sensitive RNA polymerase to which the drug binds weakly, and the dominant mutation rif D R , which codes for a rifampicin resistant RNA polymerase, the concentration of these subunits in the cell was increased 1.6 fold. Measurements made after removal of rifampicin from the cells showed that the excess and subunits did not reduce the rate of their own synthesis below normal.  相似文献   

11.
A novel syrup containing neofructo-oligosaccharides was produced from sucrose (Brix 70) by whole cells of Penicillium citrinum. The efficiency of fructo-oligosaccharides production was more than 55% and those of the main carbohydrate components, 1-kestose (Fruf 21Fruf 21 Glc), nystose (Fruf 21Fruf 21 Fruf 21 Glc) and neokestose (Fruf 26 Glc12 Fruf), were 22, 14 and 11%, respectively.  相似文献   

12.
We examined how hatchlings of the freshwater snail, Pomacea canaliculata, responded to aqueous extracts of conspecific hatchlings. Three, 3-day-old hatchlings were macerated in deionized water (1mg hatchling per 1ml water). When 0.5ml of the aqueous extract was added to a test tube containing 10 hatchlings of the same age and 50ml of water, the hatchlings in the water began to crawl out of the water within 5min. The proportion of hatchlings that crawled out of the water approached 0.6–0.9 after 1h, but gradually decreased to 0.4 after 24h. The relatedness between the live and the macerated hatchlings had no significant influence on the response. Hatchlings of egg masses obtained either in the laboratory or in the wild responded similarly to aqueous extracts of hatchlings from either egg mass. This suggests that the conditions under which the egg masses were incubated or the conditions that their parents had experienced had no effect on the hatchlings response. When compared with experiments reported on other aquatic animals, we consider the behavior of the hatchlings to be an alarm response of escaping from predators.  相似文献   

13.
The primary structures of three -amylase inhibitors (TAI, DAI, and MAI-2) consisting of glycoprotein subunits and from the respective seeds of three cultivars of Phaseolus beans, Toramame (Phaseolus vulgaris L.), Daifukumame (Phaseolus vulgaris L.), and Murasakihanamame (Phaseolus coccineus L.) were determined by sequencing the peptide fragments derived from their enzymatic digestions. Major sugar chains of the inhibitors were also assessed by analyzing glycopeptides in the enzymatic digests. The subunits, and , were shown to be composed of 76 and 139 amino acid residues, respectively, in each inhibitor. The overall amino acid sequences of the inhibitors were slightly different from one another. Furthermore, the sequence of TAI was the same as that deduced from a cDNA clone encording -amylase inhibitor-1 from the common bean (Phaseolus vulgaris L.). It was also revealed that there were two N-glycosylation sites in each -subunit: PA-derivatives of the major N-glycans were estimated to be M6B at Asn(12) and M9A at Asn(65). Each -subunit of TAI and MAI-2 had two N-glycosylation sites, while the -subunit of DAI had only one site. The major N-glycans pyridylaminated were estimated to be M3X at Asn(63) in each -subunit and M3FX at Asn(83) in -subunits of TAI and MAI-2.  相似文献   

14.
Axillary shoot induction and plant regeneration were obtained in Plantago ovata. The optimum medium for inducing axillary shoots was Murashige & Skoog (MS) medium [5] supplemented with 4.6 M kinetin and 0.05 M NAA. Rooting of shoots was best on half-strength MS medium containing 5.0 M IBA and 0.05 M kinetin. The regenerated plants were similar to the control plants in karyotypic and phenotypic details.  相似文献   

15.
Hybridizations ofElymus nutans andE. jacquemontii were carried out with one species ofPseudoroegneria (S genome), and 20Elymus species, each containing either of the SH, SY, SYH, or SYW genomes. Chromosome configurations were analysed at metaphase I of the two target taxa and their interspecific hybrids. It is concluded that (i)E. nutans is an allohexaploid containing the SYH genomes, andE. jacquemontii is an allotetraploid having the SY genomes; (ii) the genomic affinity is associated with the geographic distance between the species studied; (iii) minor genomic structural rearrangements have occurred within the hexaploid taxon ofE. nutans.  相似文献   

16.
Summary The aim of this study was to determine whether DNA variations could be detected in regenerated pea plants. Two different genotypes were analyzed by cytogenetic and molecular techniques: the Dolce Provenza cultivar and the 5075 experimental line. Dolce Provenza regenerated plants showed a reduction in DNA content, particularly at the level of unique sequences and ribosomal genes. Moreover, regeneration was associated with an increase in DNA methylation of both internal and external cytosines of the CCG sequence. On the other hand, the DNA content of the 5075 line remained stable after regeneration. DNA reduction was found only in 5075 plants regenerated from callus cultures maintained for long incubation periods (about a year). The DNA variations observed are discussed both in relation to the genotype source and the role of tissue-culture stress.  相似文献   

17.
Poly-N-acetyllactosamines provide backbone structures for functional modifications such as sialyl Lewis X. To understand how the biosynthesis of poly-N-acetyllactosamines is regulated, two branched oligosaccharides of the structure Gal1,4GlcNAc1, 6(Gal1,4GlcNAc1,2)-Man1,6Man-octyl 1 and 2 were synthesized in which one of the terminal galactose units was selectively radiolabeled. Hexasaccharides 1 and 2 were assembled from the chemically synthesized pentasaccharide precursors GlcNAc1,6(Gal1,4GlcNAc1,2)-Man1,6Man-octyl3 and Gal1,4GlcNAc1,6(GlcNAc1, 2) - Man1,6 Man-octyl 4 respectively, through treatment with UDP-1-[3H]-Gal and 1,4 galactosyltransferase. Compounds 1 and 2 were subsequently incubated with UDP-GlcNAc and the UDP-GlcNAc: Gal1-4Glc(NAc)1,3-N-acetylglucosaminyltransferase (i-GlcNAc transferase) resulting in a partial conversion to a mixture of heptasaccharides which were purified by HPLC. The branch selectivity of the addition of N-acetylglucosamine to compounds 1 and 2 was then characterized by endo--galactosidase digestion of the heptasaccharides, followed by isolation of the resultant pentasaccharides on C18 reverse-phase silica cartridges. Comparison of the amount of radiolabel to a control reaction lacking endo--galactosidase indicated the favored site of GlcNAc addition to be the lower 1,2-branch over the 1,6-branch by a 3:1 ratio.  相似文献   

18.
Morphology of freeze-etchedTreponema refringens (Nichols)   总被引:4,自引:0,他引:4  
The freeze-etch technique was used to study the morphology ofTreponema refringens (Nichols). There is a single band of cytoplasmic fibrils which follows a path in the form of a right-handed helix with a periodicity of 1500 nm around the body of the treponeme just below the cytoplasmic membrane. There are two major fracture planes, one located in the interior of the outer envelope and the second in the interior of the cytoplasmic membrane. The blebs or surface protuberances, which are quite prominent in negativestained preparations, were not evident with freeze-etch preparation, indicating they are not a part of the normal structure of this organism. The outer envelope in untreated cells was observed to closely fit the body of the treponeme, whereas the outer envelope of glutaraldehyde-treated cells had a loose, wrinkled appearance. Thus the loose-fitting outer envelope generally described for treponemes is most likely an artifact of preparation for negative-staining and thinsectioning.  相似文献   

19.
A stratagem for the synthesis ofneoglycoproteins suitable for the selective serodiagnosis of leprosy is described in which synthetic 3,6-di-O-methyl--d-glucopyranose, the epitope of phenolic glycolipid I fromMycobacterium leprae, was used. Condensation of 8-methoxycarbonyloctanol with the acetobromo derivative of 3,6-di-O-methylglucose gave 8-methoxycarbonyloctyl 2,4-di-O-acetyl-3,6-di-O-methyl--d-glucopyranoside in 65% yield, and with absolute stereospecificity for the anomer. The deacylated product was converted to the crystalline hydrazide and coupled to bovine gamma globulin, bovine serum albumin and poly-d-lysinevia intermediate acyl azide formation to produce the 8-carbonyloctyl 3,6-di-O-methyl--d-glucopyranosyl polypeptides. Theneoglycoproteins were highly sensitive in ELISA and emulated the specificity of the native glycolipid in analysis of sera from patients throughout the spectrum of leprosy and from different geographical regions. The 8-carbonyloctyl 3,6-di-O-methyl--d-glucopyranoside-bovine serum albumin was also synthesized and shown to have about one-half the activity of the -linkedneoglycoprotein. A different synthetic approach produced the 8-carbonyloctyl 4-O-(3,6-di-O-methyl--d-glucopyranosyl)--l-rhamnopyranoside-bovine serum albumin which was also highly sensitive and specific for the serodiagnosis of leprosy. The presence of the second sugar unit, similar to that in the native glycolipid but for the absence ofO-methyl groups, seemed to provide a probe with greater felicity for the serological detection of tuberculoid leprosy.Thus, the results indicate that highly sensitive and specific antigen probes for the serodiagnosis of leprosy can be constructed based only on the terminal one or two sugars of phenolic glycolipid I, and the synthetic approach leads to the formation of haptens with absolute stereospecificity.Nomenclature BGG bovine gamma globulin - PGL-I phenolic glycolipid I - PDL poly-d-lysine - PBS phophate-buffered saline - 3,6-Me2-Glc-Link-BSA 8-carbonyloctyl 3,6-di-O-methyl-glucopyranoside-bovine senalbumin - 3,6-Me2-Glc-Rha-Link-BSA 8-carbonyloctyl 4-O-(3,6-di-O-methyl--d-glucopyranosyl)--l-rhan pyranoside-BSA  相似文献   

20.
Summary Rhizoxin, an antibiotic, exhibits potent anti-mitotic activity against most eucaryotic cells including those of higher vertebrates, plants and fungi by binding to -tubulin. ThebenA gene of three independently isolated rhizoxin-resistant (Rhir) mutants ofAspergillus nidulans was cloned, sequenced and compared with that of the wild-type, rhizoxin-sensitive (Rhis) strain. In all three Rhir mutants, the AAC codon for Asn-100 of thebenA -tubulin gene was altered to ATC, coding for Ile. Sequence displacement experiments confirmed that the substitution of Ile for Asn-100 confers resistance to rhizoxin in this organism. The amino acid sequences of -tubulin surrounding the 100th amino acid residue from the N-terminus including Asn-100 are highly conserved with a few exceptions. The fission yeastSchizosaccharomyces pombe and the budding yeastSaccharomyces cerevisiae are naturally occurring Rhir organisms whose -tubulin genes encode Ile and Val respectively at the 100th amino acid residue. The Ile-100 ofS. pombe and the Val-100 ofS. cerevisiae were altered to Asn using site-directed mutagenesis and gene displacement techniques. The resultant haploid strains of these two yeasts uniquely expressing -tubulin (Asn-100) instead of -tubulin (Ile-100 or Val-100) were found to be Rhis. Haploid yeast expressing -tubulin (Asn-100) is normal except for its sensitivity to rhizoxin. These results suggest that rhizoxin resistance has a common basis in both naturally occurring species and experimentally selected mutants in the substitution of Ile or Val for Asn-100 in -tubulin.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号