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PubMed1989

Projections of the nucleus accumbens in the cat.

Due to the recent advances in knowledge on the function of the limbic system it would be wise to consider this system as being widely distributed throughout the diencephalic and mesencephalic levels as well as the forebrain. Numerous regions have been discovered that are related to the limbic structures in anatomical and functional respects. According to Koikegami et al. (1967), it would be adequate to divide this system into two main categories--the major limbic rim or the structure proper and the paralimbic structures. The former defined phylogenetically and ontogenetically as those structures around the third ventricle such as: the hippocampus, septum, dentate gyrus, fimbria hippocampi, anterior and posterior cingulate gyri, area paraolfactoria, amygdala and Diagonal Band of Broca. The paralimbic structures may represent those brain regions, which have direct connections or functional correlations with the limbic formation proper. These areas include the posterior orbital gyrus, insula, nucleus accumbens, head of the caudate, nucleus habenula, nucleus interpendencularis, nucleus pulvinaris thalami, intralaminar and anterior thalamic nucleus, preoptic area, hypothalamic nuclei, mammillary body, subthalamus, limbic midbrain area of Nauta, temporal lobe pole, superior temporal gyrus, praecuneus, nucleus dorsalis et profundis tegmenti of Gudden and claustrum. In the present paper we will deal with the projections of the nucleus accumbens. This nucleus was described by Meynert (1872) as the anterior polar region of the caudate nucleus. Kappers describes the nucleus accumbens in 1908 as the nucleus accumbens septi and considers it as a part of the striatum. Later on, the histological studies of Brochaus (1942) relate a part of the nucleus with olfactory functions, and he describes another part, which is very well developed in microsmatic mammals and in anosmic mammals like the dolphin. Szteyn (1960) describes two main areas, the accumbens septi and the accumbens caudate. Nevertheless, the accumbens constitutes a very important region of the paralimbic system and seems to play an important role in some behavioral patterns.

Animals↗

PubMed1980

Immunoglobulin diversity in the phylogenetically primitive shark, Heterodontus francisci. Suggested lack of structural variation between light chains isolated from different animals.

A two-step procedure employing gel filtration and anion exchange chromatography has been utilized to isolate LMW immunoglobulin from the horned shark, Heterodontus francisci. Light chains obtained by complete reduction and alkylation of the parent protein have been compared by several analytical techniques. Amino acid composition data implies a limited degree of variation in the light chains isolated from individual animals. Polyacrylamide gel electrophoresis of the CNBr digests of the light chains reveal indistinguishable banding profiles of the major peptides. Isoelectric focusing indicates limited heterogeneity in the light chain spectrotype and identity in the pI of the majority of bands detectable by staining. The suggested degree of structural similarity in the light chains of this phylogenetically primitive shark is discussed in terms of the evolutionary position of the species and current theories concerning the origins of structural diversity in immunoglobulins.

Amino Acids↗

PubMed2025

Inference of Cytochrome P450 Evolutionary History Using Structural and Physicochemical Metrics.

Cytochrome P450s are a superfamily of heme-binding monooxygenases involved with the detoxification of intrinsic and extrinsic toxins. They are near ubiquitous within biological domains and are found in all domains. Members of families within the superfamily are defined based on amino acid identity thresholds, with thresholds as low as 40% in some families. Relationships among Cytochrome P450 families have proven elusive due to sub-Twilight Zone interfamily identities (<30%) that result in poor multiple sequence alignment quality and thus low levels of support for downstream phylogenetic reconstructions. Despite the low identities, Cytochrome P450 structures are remarkably well conserved both within and among families. In such cases, structural phylogenetics has the potential to unveil elusive relationships because the selectively favored physicochemical properties giving rise to the structure and function of the proteins persist despite sequence-level divergence. Recently, in two separate publications, we demonstrated that by utilizing physicochemical vectors, dynamic time warping, and hierarchical clustering (PCDTW), large swaths of protein domain families and betacoronavirus receptor-binding domain clades were congruent with validated functional/structural relationships. These were important findings because anomalous sequence alignment-based maximum likelihood phylogenetic findings, which were not congruent with the known functional relationships, were resolved. That also validated the use of physicochemical vectors in making inferences about structural/functional homology. Additionally, it illuminated that the same methods might be applied to other protein families with relationships that are difficult to resolve from sequence data alone. Herein, we used Molecular Weight and Hydrophobicity Physicochemical Dynamic Time Warping (MWHP PCDTW) along with structural and sequence alignment-based phylogenetic methodologies to analyze all of the Cytochrome P450s found both in the high-fidelity Structural Classificaction of Proteins (SCOP) database and the reviewed sequences with both experimentally resolved and de novo predicted structures in the Protein Data Bank and the AlphaFold (AF) Protein Structure Database, respectively. We compared the resulting phylogenetic topologies and found that in some cases, structure-based methods may be less able to resolve random/convergent similarity than physicochemical and sequence-based methodologies. This finding agrees with previous findings that demonstrate the usefulness of physicochemical properties in resolving both random structural similarity and potentially convergent relationships.

Cytochrome P-450 Enzyme System↗

PubMed1997

Antisense micF RNA and 5'-UTR of the target ompF RNA: phylogenetic conservation of primary and secondary structures.

Outer membrane protein F (OmpF) found in E. coli and related bacteria is post-transcriptionally regulated by antisense micF RNA. During down regulation of ompF expression, micF RNA binds to the 5' UTR of ompF mRNA, blocks translation of the message, and also participates in the chemical destabilization of the ompF mRNA. Only about one third of the micF RNA sequence binds the target ompF mRNA. Phylogenetic analyses of micF RNA and ompF mRNA show: 1) a high degree of conservation of nucleotide sequence in regions of both RNAs involved in RNA/RNA interaction, 2) a low nucleotide sequence conservation but high degree of secondary structure conservation in regions of antisense and target RNAs not involved in the RNA/RNA interaction. Whereas conserved sequences are associated with RNA/RNA binding and blockage of translation, conservation of secondary structure may be related to protein interactions associated with chemical destabilization of the message.

Enterobacteriaceae↗

PubMed2004

Phylogenetic analysis and sequence comparisons of structural and non-structural SARS coronavirus proteins in Taiwan.

Taiwan experienced a large number of severe acute respiratory syndrome (SARS) viral infections between March and July 2003; by September of that year, 346 SARS cases were confirmed by RT-PCR or serological tests. In order to better understand evolutionary relationships among SARS coronaviruses (SCoVs) from different international regions, we performed phylogenetic comparisons of full-length genomic and protein sequences from 45 human SCoVs (including 12 from Taiwan) and two civet SCoVs. All the Taiwanese SARS-CoV strains which associated with nosocomial infection formed a monophyletic clade within the late phase of the SARS epidemic. This Taiwanese clade could be further divided into two epidemic waves. Taiwan SCoVs in the first wave clustered with three isolates from the Amoy Gardens housing complex in Hong Kong indicating their possible origin. Of the 45 human SCoVs, one isolate from Guangdong province, China, exhibited an extra 29-nucleotide fragment between Orf 10 and Orf 11--similar to the civet SCoV genome. Nucleotide and protein sequence comparisons suggested that all SCoVs of late epidemic came from human-to-human transmission, while certain SCoVs of early epidemic might have originated in animals.

Amino Acid Sequence↗

PubMed1995

An organelle-like small subunit ribosomal RNA gene from Babesia bovis: nucleotide sequence, secondary structure of the transcript and preliminary phylogenetic analysis.

Investigations aimed at identifying the mitochondrial genome of Babesia bovis using the polymerase chain reaction (PCR) have established the existence of an organelle-like small subunit ribosomal RNA (SSU rRNA) gene in the parasite. The sequence, compiled from three main PCR products, was 1448 bp in length (including the primer regions), had a 73% A+T content and showed significant similarity (68% sequence identity) to the "organellar" SSU rRNA gene from Plasmodium falciparum. The proposed secondary structure of the transcript showed several features which were consistent with a eubacterial origin for the organelle-like gene. The presence of putative binding sites for streptomycin and tetracycline also supported an "organellar" location for the gene and suggested that the SSU rRNA transcript is functional in protein synthesis because tetracycline has anti-babesial activity. Phylogenetic analyses based on the conserved regions of the SSU-like rRNA genes from a wide variety of organisms showed only a weak association of the babesial sequence with its mitochondrial homologues and an even weaker association with the corresponding genes of plastid origin. The origin of this organelle-like gene in B. bovis therefore remains unresolved, as is the case for its homologue from P. falciparum.

Animals↗

PubMed2026

Mitochondrial genomes of Dactylogyrus wunderi (Monopisthocotyla: Dactylogyridae): structural features, codon usage patterns, and phylogenetic implications.

BACKGROUND: Codon usage bias (CUB) is a common phenomenon reported among many species and genes, but its unique characteristics in the mitochondrial genome of class Monopisthocotyla remain unknown. METHODS: The complete mitochondrial genome of Dactylogyrus wunderi was sequenced and characterized, and the mitochondrial genome compositions and CUB of six Dactylogyrus species and 35 Monopisthocotyla species were analyzed using bioinformatics methods. RESULTS: The mitochondrial genome of D. wunderi is a typical circular structure in length of 14,920 bp. The A + T contents of the six Dactylogyrus species (58.4% ± 5.7%) were significantly lower than that of Monopisthocotyla species (71.0% ± 5.80%, p < 0.01). Neutrality plot analysis showed slopes of 0.3136 and 0.389 in the six Dactylogyrus and the 35 Monopisthocotyla species, respectively. Furthermore, 98.3% and 77.4% of the genes in the six Dactylogyrus and the Monopisthocotyla species, respectively, had effective number of codons (ENC) higher than 35, but 23.3% and 0.5% genes of ENC ratio ranged from - 0.05 to 0.05 in the six Dactylogyrus and Monopisthocotyla species. Phylogenetic analysis revealed that, within the context of the sampled taxa, the families of Monopisthocotyla were monophyletic groups, except for Ancyrocephalidae. CONCLUSIONS: The nucleotide composition had AT base bias in Monopisthocotyla, and natural selection was the main factor affecting CUB in the mitochondrial genomes of Monopisthocotyla species. These results provided insights into the factors affecting CUB in Monopisthocotyla species and deepened our insight of phylogeny, evolution, and codon usage of Monopisthocotyla.

Genome, Mitochondrial↗

PubMed1996

Cloning, functional organization, transcript studies, and phylogenetic analysis of the complete nitrogenase structural genes (nifHDK2) and associated genes in the archaeon Methanosarcina barkeri 227.

Determination of the nucleotide sequence of the nitrogenase structural genes (nifHDK2) from Methanosarcina barkeri 227 was completed in this study by cloning and sequencing a 2.7-kb BamHI fragment containing the 3' end of nifK2 and 1,390 bp of the nifE2-homologous genes. Open reading frame nifK2 is 1,371 bp long including the stop codon TAA and encodes a polypeptide of 456 amino acids. Phylogenetic analysis of the deduced amino acid sequences of the nifK2 and nifE2 gene products from M. barkeri showed that both genes cluster most closely with the corresponding nif-1 gene products from Clostridium pasteurianum, consistent with our previous analyses of nifH2 and nifD2. The nifE gene product is known to be homologous to that of nifD, and our analysis shows that the branching pattern for the nifE proteins resembles that for the nifD product (with the exception of vnfE from Azotobacter vinelandii), suggesting that a gene duplication occurred before the divergence of nitrogenases. Primer extension showed that nifH2 had a single transcription start site located 34 nucleotides upstream of the ATG translation start site for nifH2, and a sequence resembling the archaeal consensus promoter sequence [TTTA(A/T)ATA] was found 32 nucleotides upstream from that transcription start site. A tract of four T's, previously identified as a transcription termination site in archaea, was found immediately downstream of the nifK2 gene, and a potential promoter was located upstream of the nifE2 gene. Hybridization with nifH2 and nifDK2 probes with M. barkeri RNA revealed a 4.6-kb transcript from N2-grown cells, large enough to harbor nifHDK genes and their internal open reading frames, while no transcript was detected from NH4(+)-grown cells. These results support a model in which the nitrogenase structural genes in M. barkeri are cotranscribed in a single NH4(+)-repressed operon.

Base Sequence↗

PubMed1997

Mycothiol-dependent formaldehyde dehydrogenase, a prokaryotic medium-chain dehydrogenase/reductase, phylogenetically links different eukaroytic alcohol dehydrogenases--primary structure, conformational modelling and functional correlations.

Prokaryotic mycothiol-dependent formaldehyde dehydrogenase has been structurally characterized by peptide analysis of the 360-residue protein chain and by molecular modelling and functional correlation with the conformational properties of zinc-containing alcohol dehydrogenases. The structure is found to be a divergent medium-chain dehydrogenase/reductase (MDR), at a phylogenetic position intermediate between the cluster of dimeric alcohol dehydrogenases of all classes (including the human forms), and several tetrameric reductases/dehydrogenases. Molecular modelling and functionally important residues suggest a fold of the mycothiol-dependent formaldehyde dehydrogenase related overall to that of MDR alcohol dehydrogenases, with the presence of the catalytic and structural zinc atoms, but otherwise much altered active-site relationships compatible with the different substrate specificity, and an altered loop structure compatible with differences in the quaternary structure. Residues typical of glutathione binding in class-III alcohol dehydrogenase are not present, consistent with that the mycothiol factor is not closely similar to glutathione. The molecular architecture is different from that of the 'constant' alcohol dehydrogenases (of class-III type) and the 'variable' alcohol dehydrogenases (of class-I and class-II types), further supporting the unique structure of mycothiol-dependent formaldehyde dehydrogenase. Borders of internal chain-length differences between this and other MDR enzymes coincide in different combinations, supporting the concept of limited changes in loop regions within this whole family of proteins.

Actinomycetales↗

PubMed2006

Introducing SONS, a tool for operational taxonomic unit-based comparisons of microbial community memberships and structures.

The recent advent of tools enabling statistical inferences to be drawn from comparisons of microbial communities has enabled the focus of microbial ecology to move from characterizing biodiversity to describing the distribution of that biodiversity. Although statistical tools have been developed to compare community structures across a phylogenetic tree, we lack tools to compare the memberships and structures of two communities at a particular operational taxonomic unit (OTU) definition. Furthermore, current tests of community structure do not indicate the similarity of the communities but only report the probability of a statistical hypothesis. Here we present a computer program, SONS, which implements nonparametric estimators for the fraction and richness of OTUs shared between two communities.

Biodiversity↗

PubMed1990

Mutational analysis of conserved nucleotides in a self-splicing group I intron.

We have constructed all single base substitutions in almost all of the highly conserved residues of the Tetrahymena self-splicing intron. Mutation of highly conserved residues almost invariably leads to loss of enzymatic activity. In many cases, activity could be regained by making additional mutations that restored predicted base-pairings; these second site suppressors in general confirm the secondary structure derived from phylogenetic data. At several positions, our suppression data can be most readily explained by assuming non-Watson-Crick base-pairings. In addition to the requirements imposed by the secondary structure, the sequence of the intron is constrained by "negative interactions", the exclusion of particular nucleotide sequences that would form undesirable secondary structures. A comparison of genetic and phylogenetic data suggests sites that may be involved in tertiary structural interactions.

Animals↗

PubMedDate not supplied

Structure-function analysis in nuclear RNase P RNA.

Eukaryotic ribonuclease P (RNase P) enzymes require both RNA and protein subunits for activity in vivo and in vitro. We have undertaken an analysis of the complex RNA subunit of the nuclear holoenzyme in an effort to understand its structure and its similarities to and differences from the bacterial ribozymes. Phylogenetic analysis, structure-sensitive RNA footprinting, and directed mutagenesis reveal conserved secondary and tertiary structures with both strong similarities to the bacterial consensus and distinctive features. The effects of mutations in the most highly conserved positions are being used to dissect the functions of individual subdomains.

Bacteria↗

PubMed2004

Systematic analysis of snake neurotoxins' functional classification using a data warehousing approach.

MOTIVATION: Sequence annotations, functional and structural data on snake venom neurotoxins (svNTXs) are scattered across multiple databases and literature sources. Sequence annotations and structural data are available in the public molecular databases, while functional data are almost exclusively available in the published articles. There is a need for a specialized svNTXs database that contains NTX entries, which are organized, well annotated and classified in a systematic manner. RESULTS: We have systematically analyzed svNTXs and classified them using structure-function groups based on their structural, functional and phylogenetic properties. Using conserved motifs in each phylogenetic group, we built an intelligent module for the prediction of structural and functional properties of unknown NTXs. We also developed an annotation tool to aid the functional prediction of newly identified NTXs as an additional resource for the venom research community. AVAILABILITY: We created a searchable online database of NTX proteins sequences (http://research.i2r.a-star.edu.sg/Templar/DB/snake_neurotoxin). This database can also be found under Swiss-Prot Toxin Annotation Project website (http://www.expasy.org/sprot/).

Animals↗

PubMed1984

Xenopus laevis 18S ribosomal RNA: experimental determination of secondary structural elements, and locations of methyl groups in the secondary structure model.

18S ribosomal RNA from X. laevis was subjected to partial digestion with ribonucleases A or T1 under a variety of conditions, and base-paired fragments were isolated. Sequence analysis of the fragments enabled five base-paired secondary structural elements of the 18S RNA to be established. Four of these elements (covering bases 221-256, 713-757, 1494-1555 and 1669-1779) confirm our previous secondary structure predictions, whereas the fifth (comprising bases 1103-1125) represents a phylogenetically conserved "switch" structure, which can also form in prokaryotic 16S RNA. The results are incorporated into a refined model of the 18S RNA secondary structure, which also includes the locations of the many methyl groups in X. laevis 18S RNA. In general the methyl groups occur in non-helical regions, at hairpin loop ends, or at helix boundaries and imperfections. One large cluster of 2'-O-methyl groups occurs in a region of complicated secondary structure in the 5'-one third of the molecule.

Animals↗

PubMed1997

Secondary structure of the 5'-noncoding region of border disease virus genome RNAs.

The computer predicted secondary structures from the 5'-NC genome region of four border disease virus (BDV) strains collected from sheep in England and Scotland over a period 1976-1986 were prepared. The FOLD program from GCG sequence analysis software package was used for the analysis of a 243 bp RNA fragment. Two typical shapes of secondary structures were observed which contained multiple imperfect stem-loop motifs. The shape of those structures exactly fit with the grouping of BDV strains to two phylogenetic groups. Secondary structures are typical only of BDV strains and they are different from the structures prepared for NADL (BVDV) and Alfort (CSFV) strains.

Animals↗

PubMed1995

Ciliate telomerase RNA structural features.

Telomerase RNA is an integral part of telomerase, the ribonucleoprotein enzyme that catalyzes the synthesis of telomeric DNA. The RNA moiety contains a templating domain that directs the synthesis of a species-specific telomeric repeat and may also be important for enzyme structure and/or catalysis. Phylogenetic comparisons of telomerase RNA sequences from various Tetrahymena spp. and hypotrich ciliates have revealed two conserved secondary structure models that share many features. We have cloned and sequenced the telomerase RNA genes from an additional six Tetrahymena spp. (T. vorax, T. borealis, T. australis, T. silvana, T. capricornis and T. paravorax). Inclusion of these sequences, most notably that from T. paravorax, in a phylogenetic comparative analysis allowed us to more narrowly define structural elements that may be necessary for a minimal telomerase RNA. A primary sequence element, positioned 5' of the template and conserved between all previously known ciliate telomerase RNAs, has been reduced from 5'-(C)UGUCA-3' to the 4 nt sequence 5'-GUCA-3'. Conserved secondary structural features and the impact they have on the general organization of ciliate telomerase RNAs is discussed.

Animals↗

PubMed1994

Isoprenyl diphosphate synthases: protein sequence comparisons, a phylogenetic tree, and predictions of secondary structure.

Isoprenyl diphosphate synthases are ubiquitous enzymes that catalyze the basic chain-elongation reaction in the isoprene biosynthetic pathway. Pairwise sequence comparisons were made for 6 farnesyl diphosphate synthases, 6 geranylgeranyl diphosphate synthases, and a hexaprenyl diphosphate synthase. Five regions with highly conserved residues, two of which contain aspartate-rich DDXX(XX)D motifs found in many prenyltransferases, were identified. A consensus secondary structure for the group, consisting mostly of alpha-helices, was predicted for the multiply aligned sequences from amino acid compositions, computer assignments of local structure, and hydropathy indices. Progressive sequence alignments suggest that the 13 isoprenyl diphosphate synthases evolved from a common ancestor into 3 distinct clusters. The most distant separation is between yeast hexaprenyl diphosphate synthetase and the other enzymes. Except for the chromoplastic geranylgeranyl diphosphate synthase from Capsicum annuum, the remaining farnesyl and geranylgeranyl diphosphate synthases segregate into prokaryotic/archaebacterial and eukaryotic families.

Alkyl and Aryl Transferases↗

PubMed1995

Comparative anatomy of the external and middle ear of palaeognathous birds.

This study provides new anatomical data, morphometric measurements, and functional hypotheses about the middle ear of paleognathous and a basal neognathous bird. The introduction discusses current theoretical concepts and basic functional approaches in vertebrate morphology. A cautious and somewhat skeptical evaluation of the techniques used, errors made, and personal experience gained in this study forms the background of the interpretation of the structural data. The comparative discussion extracts phylogenetic information from the structural data. The external ear opening of paleognathous species is large and unprotected. The auricular feathers show no structural specialization and provide only incomplete opercularization. No muscles insert into the external ear opening. Special attention has been paid to modifications in the cassowary's skin. The skin of its head has developed cavernous blood sinuses that may be flooded and thus inflate the head during booming display. The external auditory meatus of paleognathous birds is large, bends ventrally, and reaches the tympanic membrane from the ventral side. No peculiarities can be described. The osteology of the tympanic region is described in detail. The fusion of all bony elements and the ossification of connective tissue are important features of the avian middle ear region. The fusion of bone is a necessary prerequisite for extended pneumatization. The ossification of connective tissue, however, complicates morphological description since it deviates from morphologically defined bones. Especially in the neognathous button quail, most of the ventral wall of the middle ear cavity consists of ossified connective tissue; it also includes elements of the extracolumella. The fixation of the eardrum to the bony wall of the tympanic cavity is described in detail. The fixation includes the kinetic quadrate and loose connective tissue in the ventro-lateral part of the middle ear cavity. Movements of the bill must change the tension of the eardrum and thus affect the hearing of birds. The recesses of the middle ear cavity have been investigated using X-ray computed tomography. Using this technique, subsequent three-dimensional reconstruction provides unusual and unique insights into the anatomy of such "nonstructures" as air-filled cavities. It has been shown that three tympanic recesses are a character shared by all birds. Of more functional importance is the interaural pathway provided by the anterior tympanic recess and connecting the contralateral middle ear cavities. This structure is present in all recent and mesozoic birds. It has been suggested that the interaural pathway might function as a sound pressure gradient receptor. Physiological data are controversial but in many cases supportive.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗