The EMBL data library

The HMG-1 box protein family: classification and functional relationships

The abundant and highly-conserved nucleoproteins comprising the high mobility group-1/2 (HMG-1/2) family contains two homologous basic domains of about 75 amino acids. These basic domains, termed HMG-1 boxes, are highly structured and facilitate HMG-DNA interactions. Many proteins that regulate various cellular functions involving DNA binding and whose target DNA sequences share common structural characteristics have been identified as having an HMG-1 box; these proteins include the RNA polymerase I transcription factor UBF, the mammalian testis-determining factor SRY and the mitochondrial transcription factors ABF2 and mtTF1, among others. The sequences of 121 HMG-1 boxes have been compiled and aligned in accordance with thermodynamic results from homology model building (threading) experiments, basing the alignment on structure rather than by using traditional sequence homology methods. The classification of a representative subset of these proteins was then determined using standard least-squares distance methods. The proteins segregate into two groups, the first consisting of HMG-1/2 proteins and the second consisting of proteins containing the HMG-1 box but which are not canonical HMG proteins. The proteins in the second group further segregate based on their function, their ability to bind specific sequences of DNA, or their ability to recognize discrete non-B-DNA structures. The HMG-1 box provides an excellent example of how a specific protein motif, with slight alteration, can be used to recognize DNA in a variety of functional contexts.

The sulfur controller-2 negative regulatory gene of Neurospora crassa encodes a protein with beta-transducin repeats

The sulfur regulatory system of Neurospora crassa is composed of a set of structural genes involved in sulfur catabolism controlled by a genetically defined set of trans-acting regulatory genes. These sulfur regulatory genes include cys-3+, which encodes a basic region-leucine zipper transcriptional activator, and the negative regulatory gene scon-2+. We report here that the scon-2+ gene encodes a polypeptide of 650 amino acids belonging to the expanding beta-transducin family of eukaryotic regulatory proteins. Specifically, SCON2 protein contains six repeated G beta-homologous domains spanning the C-terminal half of the protein. SCON2 represents the initial filamentous fungal protein identified in the beta-transducin group. Additionally, SCON2 exhibits a specific amino-terminal domain that potentially defines another subfamily of beta-transducin homologs. Expression of the scon-2+ gene has been examined using RNA hybridization and gel mobility-shift analysis. The dependence of scon-2+ expression on CYS3 function and the binding of CYS3 to the scon-2+ promoter indicate the presence of an important control loop within the N. crassa sulfur regulatory circuit involving CYS3 activation of scon-2+ expression. On the basis of the presence of beta-transducin repeats, the crucial role of SCON2 in the signal-response pathway triggered by sulfur limitation may be mediated by protein-protein interactions.

Homology model building of the HMG-1 box structural domain

Nucleoproteins belonging to the HMG-1/2 family possess homologous domains approximately 75 amino acids in length. These domains, termed HMG-1 boxes, are highly structured, compact, and mediate the interaction between HMG-1 box-containing proteins and DNA in a variety of biological contexts. Homology model building experiments on HMG-1 box sequences 'threaded' through the 1H-NMR structure of an HMG-1 box from rat indicate that the domain does not have rigid sequence requirements for its formation. Energy calculations indicate that the structure of all HMG-1 box domains is stabilized primarily through hydrophobic interactions. We have found structural relationships in the absence of statistically significant sequence similarity, identifying several candidate proteins which could possibly assume the same three-dimensional conformation as the rat HMG-1 box motif. The threading technique provides a method by which significant structural similarities in a diverse protein family can be efficiently detected, and the 'structural alignment' derived by this method provides a rational basis through which phylogenetic relationships and the precise sites of interaction between HMG-1 box proteins and DNA can be deduced.

Development of a PCR-based technique for detection of Helicobacter pylori

A primer-set was designed for specific detection of genes that encode for 16S rRNA of Helicobacter pylori, using direct polymerase chain reaction (PCR). The primers were selected in the hypervariable regions, derived from a complete small subunit 16S rRNA sequence of the reference strain H. pylori CCUG 17874. The primer-set amplified a 537 base pair (bp) sequence specifically from chromosomal H. pylori DNA. Amplification of purified chromosomal H. pylori DNA was achieved at concentrations as low as 1 femto gram (fg), equivalent to 5 bacteria. Furthermore, as few as 1 lysed H. pylori cell was detected by this PCR technique. The specificity of the primers was 100%, since purified chromosomal DNA was detected from all 32 various H. pylori isolates, whereas no other bacteria species were detected, whether related to Helicobacter or not. The 16S rDNA primers successfully detected H. pylori in antral biopsy specimens collected from infected patients.

VISTAS: a package for VIsualizing STructures and sequences of proteins

VISTAS is a suite of programs for protein sequence and structure analysis. The system allows the simultaneous display, in separate windows, of multiple sequence alignments, of known or model 3D structures, and of 2D graphic representations of sequence and/or alignment properties. The displays are fully integrated, and therefore manipulations in one window can be reflected in each of the others. Beyond its display facilities, VISTAS brings together a number of existing tools under a single, user-friendly umbrella: these include a fully functional interactive color alignment procedure, conserved motif selection, a range of database-scanning routines, and interactive access to the OWL composite sequence database and to the PRINTS protein fingerprint database. Exploration of the sequence database is thus straightforward, and predefined structural motifs from the fingerprint database may be readily visualized. Of particular note is the ability to calculate conservation criteria from sequence alignments and to display the information in a 3D context: this renders VISTAS a powerful tool for aiding mutagenesis studies and for facilitating refinement of molecular models.

Dissecting titin into its structural motifs: identification of an alpha-helix motif near the titin N-terminus

Titin, also known as connectin, is a giant modular protein specifically found in vertebrate striated muscle. Since the huge size of titin does not allow a direct structure determination, we have started a long-term project to characterize the protein by cutting it into smaller domains or structural units. The major part of the titin sequence is assembled by modules approximately 100 amino acids long that belong to two major protein superfamilies. Most of these modules are linked together by stretches of variable length with unique sequence. No direct structural characterization has been achieved so far for any of these linkers. We present here a study of a stretch located in the titin N-terminus and part of a linker between two modules. Our attention was drawn toward this region because it shows 100% probability to form a coiled coil when analyzed by a prediction program. A synthetic 38 amino acid peptide spanning such a sequence was studied in aqueous solution by circular dichroism, nuclear magnetic resonance, and analytical ultracentrifugation at various pH, salt, and peptide concentrations. Under all conditions, it shows a strong tendency to form alpha-helical structures. In the presence of salt, this conformation is associated with the formation of helical bundles below pH 5. Above pH 5, any aggregate breaks, and the titin peptide is a monomeric helix in equilibrium with its random coil conformation. We discuss the factors which stabilize the helical conformation and the possible role of this stretch in vivo.

Nucleotide sequence and analysis of the centromeric region of yeast chromosome IX

We have determined the nucleotide sequence of a cosmid (pIX338) containing the centromere region of yeast (Saccharomyces cerevisiae) chromosome IX. The complete nucleotide sequence of 33.8 kb was obtained by using an efficient directed sequencing strategy in combination with automated DNA sequencing on the A.L.F. DNA sequencer. Sequence analysis revealed the presence of 17 open reading frames (ORFs), four of them previously known yeast genes (sly12, pan1, sts1 and prl1), a tRNA gene and the centromere motif. Exhaustive database searches detected sequence homologues of known function for as many as 14 of the 17 ORFs. These include a mammalian tyrosine kinase substrate; the Escherichia coli cell cycle protein MinD; the human inositol polyphosphate-5-phosphatase (gene OCRL) involved in Lowe's syndrome, a developmental disorder; and helicases, for which the new yeast member defines a distinct DEAD/H-box subfamily. A surprisingly large fraction of the ORFs (at least six out of 17) in the centromeric region are apparently involved in RNA or DNA binding.

16S rDNA sequence and phylogenetic position of an uncultivated spirochete from the hindgut of the termite Mastotermes darwiniensis Froggatt

We have analyzed the 16S rDNA sequence and the phylogenetic position of an uncultivated spirochete from the hindgut contents of the Australian termite Mastotermes darwiniensis Froggatt. The 16S rRNA genes of bacteria from the hindgut contents of Mastotermes darwiniensis were amplified by polymerase chain reaction. The amplification products were cloned and sequenced. The sequences were compared to known homologous primary structures. Two of the clones (MDS1 and MDS3) had an insert of 1498 nucleotides showing typical signatures of spirochete 16S rRNA sequences. The sequences of the two clones were most similar to the 16S rRNA sequence of Spirochaeta stenostrepta (89.8%) and Treponema sp. strain H1 (90.7%). Phylogenetical analysis positioned the hindgut spirochete sequence with that of the free-living anaerobic Spirochaeta stenostrepta and Treponema sp. strain H1 as its nearest relatives within the cluster of the spirochetes. We conclude that analyzed SSU rDNA sequences originate from a spirochete related to the genus Treponema. It is possibly one of the uncultivated unique spirochetes symbiotic in termite hindguts.

Biased distribution of adenine and thymine in gene nucleotide sequences

We analyzed occurrences of bases in 20,352 introns, exons of 25,574 protein-coding genes, and among the three codon positions in the protein-coding sequences. The nucleotide sequences originated from the whole spectrum of organisms from bacteria to primates. The analysis revealed the following: (1) In most exons, adenine dominates over thymine. In other words, adenine and thymine are distributed in an asymmetric way between the exon and the complementary strand, and the coding sequence is mostly located in the adenine-rich strand. (2) Thymine dominates over adenine not only in the strand complementary to the exon but also in introns. (3) A general bias is further revealed in the distribution of adenine and thymine among the three codon positions in the exons, where adenine dominates over thymine in the second and mainly the first codon position while the reverse holds in the third codon position. The product (A1/T1)x(A2/T2)x(T3/A3) is smaller than one in only a few analyzed genes.

The SBASE protein domain library, release 3.0: a collection of annotated protein sequence segments

SBASE 3.0 is the third release of SBASE, a collection of annotated protein domain sequences. SBASE entries represent various structural, functional, ligand-binding and topogenic segments of proteins as defined by their publishing authors. SBASE can be used for establishing domain homologies using different database-search tools such as FASTA [Lipman and Pearson (1985) Science, 227, 1436-1441], and BLAST3 [Altschul and Lipman (1990) Proc. Natl. Acad. Sci. USA, 87, 5509-5513] which is especially useful in the case of loosely defined domain types for which efficient consensus patterns can not be established. The present release contains 41,749 entries provided with standardized names and cross-referenced to the major protein and nucleic acid databanks as well as to the PROSITE catalogue of protein sequence patterns. The entries are clustered into 2285 groups using the BLAST algorithm for computing similarity measures. SBASE 3.0 is freely available on request to the authors or by anonymous 'ftp' file transfer from < ftp.icgeb.trieste.it >. Individual records can be retrieved with the gopher server at < icgeb.trieste.it > and with a www-server at < http:@www.icgeb.trieste.it >. Automated searching of SBASE by BLAST can be carried out with the electronic mail server < sbase@icgeb.trieste.it >. Another mail server < domain@hubi.abc.hu > assigns SBASE domain homologies on the basis of SWISS-PROT searches. A comparison of pertinent search strategies is presented.

The PIR-International Protein Sequence Database

PIR-International is an association of macromolecular sequence data collection centers dedicated to fostering international cooperation as an essential element in the development of scientific databases. A major objective of PIR-International is to continue the development of the Protein Sequence Database as an essential public resource for protein sequence information. This paper briefly describes the architecture of the Protein Sequence Database and how it and associated data sets are distributed and can be accessed electronically.

The European Bioinformatics Institute (EBI) databases

This paper describes the databases and services of the European Bioinformatics Institute (EBI). In collaboration with DDBJ and GenBank/NCBI, the EBI maintains and distributes the EMBL Nucleotide Sequence Database, Europe's primary nucleotide sequence data resource. The EBI also maintains and distributes the SWISS-PROT Protein Sequence Database, in collaboration with Amos Bairoch of the University of Geneva. Over thirty additional specialist molecular biology databases, as well as software and documentation of interest to molecular biologists, are also available. The EBI network services include database searching, entry retrieval, and sequence similarity searching facilities.

Database on the structure of small ribosomal subunit RNA

The database on small ribosomal subunit RNA structure contains (June 1994) 2824 nucleotide sequences. All these sequences are stored in the form of an alignment based on the adopted secondary structure model, which in turn is corroborated by the observation of compensating substitutions in the alignment. The complete database is made available to the scientific community through anonymous ftp on our server in Antwerp. A special effort was made to improve electronic retrieval and a program is supplied that allows to create different file formats. The database can also be obtained from the EMBL nucleotide sequence library.

ECD--a totally integrated database of Escherichia coli K12

We have compiled the DNA sequence data for E. coli available from the GENBANK and EMBL data libraries and independently from the literature. Starting with this update of our Escherichia coli database (ECD release 20) we provide major changes compared to previous issues. This update not only represents another substantial increase in sequence information, it also allows now to find the exact physical location of each individual gene or regulatory region, even regarding discrepancies in nomenclature. In order to save space this printed version does not contain the database itself anymore, but we provide several examples. The complete database is publically available in electronic form together with a self explaining application program or as a flat file. The complete compilation including a full set of genetic map data and the E. coli protein index can be obtained in machine readable form from the EMBL data library as a part of the CD-ROM issue of the EMBL sequence database, released and updated every three months. After deletion of all detected overlaps a total of 2,878,364 individual bp is found to be determined till the end of June 1994. This corresponds to a total of 60.98% of the entire E. coli chromosome consisting of about 4,720 kbp. This number may actually be higher by 9161 bp derived from other strains of E. coli.

The ENZYME data bank

The ENZYME data bank is a repository of information relative to the nomenclature of enzymes. It is primarily based on the recommendations of the Nomenclature Committee of the International Union of Biochemistry and Molecular Biology (IUBMB) and it contains the following data for each type of characterized enzyme for which an EC (Enzyme Commission) number has been provided: EC number Recommended name Alternative names (if any) Catalytic activity Cofactors (if any) Pointers to the SWISS-PROT protein sequence entrie(s) that correspond to the enzyme (if any) Pointers to human disease(s) associated with a deficiency of the enzyme (if any).

The SWISS-PROT protein sequence data bank: current status

SWISS-PROT is an annotated protein sequence database established in 1986 and maintained collaboratively, since 1988, by the Department of Medical Biochemistry of the University of Geneva and the EMBL Data Library. The SWISS-PROT protein sequence data bank consist of sequence entries. Sequence entries are composed of different lines types, each with their own format. For standardization purposes the format of SWISS-PROT follows as closely as possible that of the EMBL Nucleotide Sequence Database. A sample SWISS-PROT entry is shown in Figure 1.

Database on the structure of large ribosomal subunit RNA

A database on large ribosomal subunit RNA is made available. It contains 258 sequences. It provides sequence, alignment and secondary structure information in computer-readable formats. Files can be obtained using ftp.

Database of p53 gene somatic mutations in human tumors and cell lines

A data base is described in which over 2,500 mutations in the p53 gene of human tumors and tumor cell lines are compiled from a systematic search of reports published before 1 January 1994. Data from 1994 are being added intermittently, with a systematic search and update scheduled for December, 1994. The compilation has been deposited with the EMBL Data Library and is available in electronic form free of charge. This report contains a rationale for the compilation, a brief summary of the major findings and a description of the data base.

The Ribosomal Database Project

The Ribosomal Database Project (RDP) is a curated database that offers ribosome-related data, analysis services, and associated computer programs. The offerings include phylogenetically ordered alignments of ribosomal RNA (rRNA) sequences, derived phylogenetic trees, rRNA secondary structure diagrams, and various software for handling, analyzing and displaying alignments and trees. The data are available via anonymous ftp (rdp.life.uiuc.edu), electronic mail (server/rdp.life.uiuc.edu) and gopher (rdpgopher.life.uiuc.edu). The electronic mail server also provides ribosomal probe checking, approximate phylogenetic placement of user-submitted sequences, screening for chimeric nature of newly sequenced rRNAs, and automated alignment.

Detection of dsRNA-binding domains in RNA helicase A and Drosophila maleless: implications for monomeric RNA helicases

Searches with dsRNA-binding domain profiles detected two copies of the domain in each of RNA helicase A, Drosophila maleless and C. elegans ORF T20G5-11 (of unknown function). RNA helicase A is unusual in being one of the few characterised DEAD/DExH helicases that are active as monomers. Other monomeric DEAD/DExH RNA helicases (p68, NPH-II) have domains that match another RNA-binding motif, the RGG repeat. The DEAD/DExH domain appears to be insufficient on its own to promote helicase activity and additional RNA-binding capacity must be supplied either as domains adjacent to the DEAD/DExH-box or by bound partners as in the eIF-4AB dimer. The presence or absence of extra RNA-binding domains should allow classification of DEAD/DExH proteins as monomeric or multimeric helicases.

Evidence for a protein domain superfamily shared by the cyclins, TFIIB and RB/p107

Cyclins, TFIIB and RB play major roles in cell cycle and/or gene regulation. Earlier work has suggested common ancestry for the TFIIB repeats and RB pocket B which share 20% sequence identity. We now report that database searches with profiles based on a multiple alignment of cyclin core regions (the 'cyclin box') detect the TFIIB repeats with equivalent scores to divergent cyclins. Several features of the sequences support the notion of common ancestry: e.g. cyclins A/B, C and D share approximately 20-30% identity but each have approximately 15-20% identity with vertebrate TFIIB, showing that conserved cyclin features underlie the match. These results suggest the presence of a domain superfamily, which we term the TR domain, in nuclear regulatory proteins belonging to the TFIIB, cyclin and RB families, that has been duplicated many times during eukaryotic evolution. The TR domain appears to function in protein-protein interactions.

Protein sequence comparisons: searching databases and aligning sequences

As the explosive growth of sequence databases continues, both the content of these databases and the best strategies for exploiting them are changing. Remarkable improvements in the performance of microcomputers have put very sophisticated tools within the reach of all investigators. New scoring schemes have improved the sensitivity of searching regimens and the accuracy of alignments.

Issues in searching molecular sequence databases

Sequence similarity search programs are versatile tools for the molecular biologist, frequently able to identify possible DNA coding regions and to provide clues to gene and protein structure and function. While much attention had been paid to the precise algorithms these programs employ and to their relative speeds, there is a constellation of associated issues that are equally important to realize the full potential of these methods. Here, we consider a number of these issues, including the choice of scoring systems, the statistical significance of alignments, the masking of uninformative or potentially confounding sequence regions, the nature and extent of sequence redundancy in the databases and network access to similarity search services.

Nucleic acid sequence analysis software packages

Software packages have made sequence analysis easier and more accessible to research scientists in many fields. The majority of these packages are routinely upgraded to include improved and innovative programs for primer design, sequence assembly and improvements in database searching programs. The interfaces of many packages have also been improved, greatly facilitating their use. In the future, researchers can expect to be able to access a growing number of network applications (e.g. database searching and exon prediction programs) from within software packages, making them accessible in familiar formats. Increased network access from within software packages will also make more databases, and more frequently updated databases, available to a larger research community.

SWISS-2DPAGE: a database of two-dimensional gel electrophoresis images

This publication presents the SWISS-2DPAGE database which gathers data on proteins identified on various two-dimensional polyacrylamide gel electrophoresis (2-D PAGE) maps. Each SWISS-2DPAGE entry contains data on one protein, including mapping procedures, physiological and pathological data and bibliographical references, as well as several 2-D PAGE images showing the protein location. Links are also provided to other databases such as SWISS-PROT, EMBL, PROSITE and OMIM. The database has been set up on a server which may be accessed from any computer connected to the internet and it also makes it possible to display the theoretical location of proteins, the positions of which are not yet known on the 2-D PAGE.

The use of reverse transcriptase-polymerase chain reaction (RT-PCR) to investigate specific gene expression in multidrug-resistant cells

Expression of specific genes at the level of mRNA can be studied using techniques such as Northern blot, slot/dot blot, RNase protection assay, in situ hybridisation and RT-PCR. In this article these methods of analysis are compared; RT-PCR offers higher levels of specificity and sensitivity than traditional methods of RNA analysis and as such has become the method of choice for the study of gene expression. The RT-PCR technique is described in detail with sections dealing with RNA extraction, choice of primers (including the use of cDNA sequence data bases), PCR and RT-PCR protocols in addition to the limitations of the method. The study of one particular mRNA transcript (MDR1) using RT-PCR is discussed in detail. Recently described methods for quantitation of PCR products are discussed. Quantitative PCR would appear to offer a method of studying gene expression in a more extensive way than has been possible to date.