促葡萄糖转运蛋白基因家族的分子进化研究

葡萄糖转运蛋白是一个在结构上相似功能上不同的多基因家族（ＧＬＵＴ１－ＧＬＵＴ５）。由于这一组蛋白和体内的葡萄糖利用有关,因此被认为是糖尿病胰岛素抵抗（抗性）的一个候选基因。本文比较了不同种生物这一基因家族的氨基酸和核苷酸顺序;推测了亲水性和疏水性分布;计算了蛋白质和核苷酸的进化距离,并在此基础上构建了分子进化树。研究表明：这一基因家族具有高度的同源性、极为相似的亲水性和疏水性分布以及结构的对称性。提示这一基因家族起源于一个共同的祖先并可能通过基因的重复而形成。这一进化机制可能有利于氨基酸结构的稳定及抵抗突变的作用。由于邻元法构建的进化树其分支长度存在差异,提示在这一基因家族的进化过程中,各分支上的进化速率并不相同。蛋白质进化距离和核苷酸进化距离所构建进化树的差异提示了在基因组中可能存在隐匿替换。两种方法构建的进化树都提示了ＧＬＵＴ１、３、４在结构和功能上要更为保守。     

Comparative studies on the dynamics of crosslinked insulin

Molecular dynamics simulations were carried out on an insulin crosslinked between the N-terminal A chain and the C-terminal B chain to form a so-called mini-proinsulin: N -^A1-N -^B29-diaminosuberoyl insulin (DASI). To investigate the influence of crosslinking on the dynamics of the insulin moiety, the bridge was removed from a transient DASI structure and simulation was carried on independently with the then unlinked (ULKI) as well as with the crosslinked species. The effects of crystal packing and quaternary interactions were checked by simulating both types of monomers and dimers known from the hexamer structure. All simulations were compared to previous ones of native insulin. DASI shows general similarity to the native simulations in most parts of the structure. Deviations are visible in the segments to which the bridge is directly connected, i.e. their flexibility is reduced. Upon removal of the bridge the ULKI simulations reapproach those of native insulin. The influence of the bridge spreads over the whole molecule, but all of its main structural features remain intact. The simulations suggest that the displacement of the C-terminal B chain of native insulin, considered important for receptor interaction, is prevented by the bridge, which also partially shields some binding residues. This is in accordance with the poor biological potency of A1-B29-crosslinked insulins.Abbreviations DASI-insulin(DASI) bovineN -^A1-N -^B29-di-aminosuberoyl insulin - ULK-insulin (ULKI) Native beef insulin with the bridge of DASI removed     

Generic level relationships of the papionini (cercopithecoidea)

Phylogenetic hypotheses for the Old World monkey tribe Papionini based on molecular data are incongruent with those inferred from previous morphological analyses. Morphologists have often inferred a close relationship between Mandrillus and Papio based on their overall similarity. Theropithecus has been variously proposed to be either quite distantly related to these two genera, their sister taxon, or anywhere in between. Molecular and chromosomal analyses on the other hand unambiguously group Theropithecus and Papio together to the exclusion of Mandrillus. Additionally, molecular and chromosomal analyses reveal that mangabeys (Cerocebus) are paraphyletic. Morphologists have acknowledged this possibility resurrecting the genus name Lophocebus for one group of mangabeys. A review and reanalysis of the morphological characters put forth by various researchers find little to contradict the consensus phylogeny derived from analysis of chromosomal banding, nuclear RNA restriction mapping, alpha and beta hemoglobin sequences, albumin and transferrin microcomplement fixation, DNA-DNA hybridization, repetitive DNA patterns, immunodiffusion, hemoglobin and adenylate kinase isozymes, and mitochondrial cytochrome oxidase subunit II DNA sequences. © 1994 Wiley-Liss, Inc.     

SUBSTITUTION PROCESSES IN MOLECULAR EVOLUTION. II. EXCHANGEABLE MODELS FROM POPULATION GENETICS

Substitution processes are of two sorts: origination processes record the times at which nucleotide mutations that ultimately fix in the population first appear, and fixation processes record the times at which they actually fix. Substitution processes may be generated by combining models of population genetics—here the symmetrical-neutral, overdominance, underdominance, TIM, and SAS-CFF models—with the infinite-sites, no-recombination model of the gene. This paper is mainly concerned with a computer simulation study of these substitution processes. The rate of substitution is shown to be remarkably insensitive to the strength of selection for models with strong balancing selection caused by the genealogical drift of mutations through alleles held in the population by selection. The origination process is shown to be more regular than Poisson for the overdominance, TIM, and SAS-CFF models but more clustered for the underdominance model. A class of point processes called Sawyer processes is introduced to help explain these observations as well as the observation that the times between successive originations are nearly uncorrelated. Fixation processes are shown to be more complex than origination processes, with regularly spaced bursts of multiple fixations. An approximation to the fixation process is described. One important conclusion is that protein evolution is not easily reconciled with any of these models without adding perturbations that recur on a time scale that is commensurate with that of molecular evolution.     

P-type ATPases of eukaryotes and bacteria: Sequence analyses and construction of phylogenetic trees

The amino acid sequences of 47 P-type ATPases from several eukaryotic and bacterial kingdoms were divided into three structural segments based on individual hydropathy profiles. Each homologous segment was (1) multiply aligned and functionally evaluated, (2) statistically analyzed to determine the degrees of sequence similarity, and (3) used for the construction of parsimonious phylogenetic trees. The results show that all of the P-type ATPases analyzed comprise a single family with four major clusters correlating with their cation specificities and biological sources as follows: cluster 1: Ca²⁺-transporting ATPases; cluster 2: Na⁺- and gastric H⁺-ATPases; cluster 3: plasma membrane H⁺-translocating ATPases of plants, fungi, and lower eukaryotes; and cluster 4: all but one of the bacterial P-type ATPases (specific for K⁺, Cd²⁺, Cu²⁺ and an unknown cation). The one bacterial exception to this general pattern was the Mg²⁺-ATPase of Salmonella typhimurium, which clustered with the eukaryotic sequences. Although exceptions were noted, the similarities of the phylogenetic trees derived from the three segments analyzed led to the probability that the N-terminal segments 1 and the centrally localized segments 2 evolved from a single primordial ATPase which existed prior to the divergence of eukaryotes from prokaryotes. By contrast, the C-terminal segments 3 appear to be eukaryotic specific, are not found in similar form in any of the prokaryotic enzymes, and are not all demonstrably homologous among the eukaryotic enzymes. These C-terminal domains may therefore have either arisen after the divergence of eukaryotes from prokaryotes or exhibited more rapid sequence divergence than either segment 1 or 2, thus masking their common origin. The relative rates of evolutionary divergence for the three segments were determined to be segment 2 < segment 1 < segment 3. Correlative functional analyses of the most conserved regions of these ATPases, based on published site-specific mutagenesis data, provided preliminary evidence for their functional roles in the transport mechanism. Our studies define the structural and evolutionary relationships among the P-type ATPases. They should provide a guide for the design of future studies of structure-function relationships employing molecular genetic, biochemical, and biophysical techniques. Correspondence to: M.H. Saier, Jr.     

Genetic mapping of turnip mosaic virus resistance in Lactuca sativa

Presence of the dominant Tu gene in Lactuca sativa is sufficient to confer resistance to infection by turnip mosaic virus (TuMV). In order to obtain an immunological assay for the presence of TuMV in inoculated plants, the TuMV coat protein (CP) gene was cloned by amplification of a cDNA corresponding to the viral genome using degenerate primers designed from conserved potyvirus CP sequences. The TuMV CP was overexpressed in Escherichia coli, and polyclonal antibodies were produced. To locate Tu on the L. sativa genetic map, F₃ families from a cross between cvs Cobbham Green (resistant to TuMV) and Calmar (susceptible) were genotyped for Tu. Families known to be recombinant in the region containing Tu were infected with TuMV and tested by the indirect enzyme-linked immunosorbent assay (ELISA) using the anti-CP serum. This assay placed Tu between two random amplified polymorphic DNA (RAPD) markers and 3.2 cM from Dm5/8 (which confers resistance to Bremia lactucae). Also, bulked segregant analysis was used to screen for additional RAPD markers tightly linked to the Tu locus. Five new markers linked to Tu were identified in this region, and their location on the genetic map was determined using informative recombinants in the region. Six markers were identified as being linked within 2.5 cM of Tu.     

Evaluation of “sequence-tagged-site” PCR products as molecular markers in wheat

The polymerase chain reaction (PCR) is an attractive technique for many genome mapping and characterization projects. One PCR approach which has been evaluated involves the use of randomly amplified polymorphic DNA (RAPD). An alternative to RAPDs is the sequence-tagged-site (STS) approach, whereby PCR primers are designed from mapped low-copy-number sequences. In this study, we sequenced and designed primers from 22 wheat RFLP clones in addition to testing 15 primer sets that had been previously used to amplify DNA sequences in the barley genome. Our results indicated that most of the primers amplified sequences that mapped to the expected chromosomes in wheat. Additionally, 9 of 16 primer sets tested revealed polymorphisms among 20 hexaploid wheat genotypes when PCR products were digested with restriction enzymes. These results suggest that the STS-based PCR analysis will be useful for generation of informative molecular markers in hexaploid wheat.Contribution no. J-2833 of the Montana Agric Exp Stn     

Interpretation of randomly amplified polymorphic DNA marker data for fingerprinting sweet potato (Ipomoea batatas L.) genotypes

In this paper we present a method for the generation of randomly amplified polymorphic DNA (RAPD) markers for sweet potato. These were applied to produce genetic fingerprints of six clonal cultivars and to estimate genetic distances between these cultivars. The level of polymorphism within the species was extremely high. From the 36-decamer random primers used, 170 fragments were amplified, of which 132 (77.6%) were polymorphic. Ten primers resulted in no detected amplification. Of the remaining 26 primers for which amplification was achieved, only one did not reveal polymorphism. Six primers used alone enabled the discrimination of all six genotypes. Pattern analysis, which employed both a classification and ordination method, enabled the grouping of cultivars and the identification of primers which gave greatest discrimination among the cultivars.     

QTL analysis: a simple ‘marker-regression’ approach

A method to locate quantitative trait loci (QTL) on a chromosome and to estimate their additive and dominance effects is described. It applies to generations derived from an F₁ by selfing or backcrossing and to doubled haploid lines, given that marker genotype information (RFLP, RAPD, etc.) and quantitative trait data are available. The method involves regressing the additive difference between marker genotype means at a locus against a function of the recombination frequency between that locus and a putative QTL. A QTL is located, as by other regression methods, at that point where the residual mean square is minimised. The estimates of location and gene effects are consistent and as reliable as conventional flanking-marker methods. Further applications include the ability to test for the presence of two, or more, linked QTL and to compare different crosses for the presence of common QTL. Furthermore, the technique is straightforward and may be programmed using standard pc-based statistical software.