Biomedical subjects

K J Addess

Publications and source records attributed to K J Addess.

8 recordsLinked to original sources

PubMed2000

MMDB: 3D structure data in Entrez.

Three-dimensional structures are now known for roughly half of all protein families. It is thus quite likely, in searching sequence databases, that one will encounter a homolog with known structure and be able to use this information to infer structure-function properties. The goal of Entrez's 3D structure database is to make this information accessible and useful to molecular biologists. To this end, Entrez's search engine provides three powerful features: (i) Links between databases; one may search by term matching in Medline((R)), for example, and link to 3D structures reported in these articles. (ii) Sequence and structure neighbors; one may select all sequences similar to one of interest, for example, and link to any known 3D structures. (iii) Sequence and structure visualization; identifying a homolog with known structure, one may view a combined molecular-graphic and alignment display, to infer approximate 3D structure. Entrez's MMDB (Molecular Modeling DataBase) may be accessed at: http://www.ncbi.nlm.nih.gov/Entrez/structure.html

Amino Acid Sequence↗

PubMed1999

MMDB: Entrez's 3D structure database.

The three dimensional structures for representatives of nearly half of all protein families are now available in public databases. Thus, no matter which protein one investigates, it is increasingly likely that the 3D structure of a homolog will be known and may reveal unsuspected structure-function relationships. The goal of Entrez's 3D-structure database is to make this information accessible and usable by molecular biologists (http://www.ncbi.nlm.nih.gov/Entrez). To this end Entrez provides two major analysis tools, a search engine based on sequence and structure 'neighboring' and an integrated visualization system for sequence and structure alignments. From a protein's sequence 'neighbors' one may rapidly identify other members of a protein family, including those where 3D structure is known. By comparing aligned sequences and/or structures in detail, using the visualization system, one may identify conserved features and perhaps infer functional properties. Here we describe how these analysis tools may be used to investigate the structure and function of newly discovered proteins, using the PTEN gene product as an example.

Amino Acid Sequence↗

PubMed1997

Structure and dynamics of the iron responsive element RNA: implications for binding of the RNA by iron regulatory binding proteins.

The iron responsive element (IRE) is a approximately 30 nucleotide RNA hairpin that is located in the 5' untranslated region of all ferritin mRNAs and in the 3' untranslated region of all transferrin receptor mRNAs. The IREs are bound by two related IRE-binding proteins (IRPs) which help control intracellular levels of iron by regulating the expression of both ferritin and transferrin receptor genes. Multi-dimensional NMR and computational approaches were used to study the structure and dynamics of the IRE RNA in solution. The NMR data are consistent with formation of A-form helical stem regions, a one-base internal bulge and a Watson-Crick C.G base-pair between the first and fifth nucleotides in the loop. A superposition of refined structures indicates that the conserved C in the internal bulge, and three residues in the six-nucleotide hairpin loop are quite dynamic in this RNA. The structural roles of the stems, the loop and the bulge in the function of the IRE RNA and in possible interactions with the iron regulatory protein are discussed.

Base Sequence↗

PubMed1994

NMR investigation of Hoogsteen base pairing in quinoxaline antibiotic--DNA complexes: comparison of 2:1 echinomycin, triostin A and [N-MeCys3,N-MeCys7] TANDEM complexes with DNA oligonucleotides.

Hoogsteen base pairs have been demonstrated to occur in base pairs adjacent to the CpG binding sites in complexes of triostin A and echinomycin with a variety of DNA oligonucleotides. To understand the relationship of these unusual base pairs to the sequence specificity of these quinoxaline antibiotics, the conformation of the base pairs flanking the YpR binding sites of the 2:1 drug-DNA complexes of triostin A with [d(ACGTACGT)]2 and of the TpA specific [N-MeCys3, N-MeCys7] TANDEM with [d(ATACGTAT)]2 have been studied by 1H NMR spectroscopy. In both the 2:1 triostin A-DNA complex and the 2:1 [N-MeCys3, N-MeCys7] TANDEM-DNA complex, the terminal A.T base pairs are Hoogsteen base paired with the 5' adenine in the syn conformation. This indicates that both TpA specific and CpG specific quinoxaline antibiotics are capable of inducing Hoogsteen base pairs in DNA. However, in both 2:1 complexes, Hoogsteen base pairing is limited to the terminal base pairs. In the 2:1 triostin A complex, the internal adenines are anti and in the 2:1 [N-MeCys3, N-MeCys7] TANDEM-DNA complex, the internal guanines are anti regardless of pH, which indicates that the central base pairs of both complexes form Watson-Crick base pairs. This indicates that the sequence dependent nature of Hoogsteen base pairing is the same in TpA specific and CpG specific quinoxaline antibiotic-DNA complexes. We have calculated a low resolution three-dimensional structure of the 2triostin A-[d(ACGTACGT)]2 complex and compared it with other CpG specific quinoxaline antibiotic-DNA complexes. The role of stacking in the formation of Hoogsteen base pairs in these complexes is discussed.

Anti-Bacterial Agents↗

PubMed1994

Sequence specificity of quinoxaline antibiotics. 1. Solution structure of a 1:1 complex between triostin A and [d(GACGTC)]2 and comparison with the solution structure of the [N-MeCys3,N-MeCys7]TANDEM-[d(GATATC)]2 complex.

Triostin A, a naturally occurring quinoxaline antibiotic that contains N-methyl groups on the valine and cysteine residues, binds sequence specifically to DNA at NCGN sites. [N-MeCys3,N-MeCys7]-TANDEM (CysMeTANDEM), a synthetic quinoxaline antibiotic, differs in its chemical structure from triostin A only at the valine residues, which contain no N-methyl substituents. CysMeTANDEM has a sequence specificity different from triostin A, binding specifically to DNA at NTAN sites. To understand the factors that determine the sequence specificity of these quinoxaline antibiotics, the solution structure of a 1:1 complex of triostin A with the DNA hexamer [d(GACGTC)]2 has been determined using NMR-derived distance and dihedral angle restraints. The solution structure of the triostin A-[d(GACGTC)]2 complex is compared directly to the solution structure of a 1:1 complex of CysMeTANDEM with [d(GATATC)]2 and is also compared to the crystal structure of 2:1 complex of triostin A with [d(CGTACG)]2. Triostin A binds to [d(GACGTC)]2 as a bis-intercalator around the CpG step, and the peptide ring of the drug binds in the minor groove of the DNA. The central C.G base pairs of the complex are underwound with an average helical twist angle of approximately -9.0 degrees and buckle inward by about 25 degrees. There are intermolecular hydrogen bonds between each of the Ala NH and the GN3 protons of the CpG binding site. Similar structural features are observed in the solution structure of the CysMeTANDEM-[d(GATATC)]2 complex. However, in the structure of the triostin A-[d(GACGTC)]2 complex, two intermolecular hydrogen bonds between each of the Ala CO oxygens of the drug and the 2-amino protons of guanine are observed. These hydrogen bonds do not form in the CysMeTANDEM-DNA complex. Instead, CysMeTANDEM contains two intramolecular hydrogen bonds between the Ala CO atoms and the Val amide protons, making the Ala CO atoms unavailable to form two intermolecular hydrogen bonds. The role of these intermolecular hydrogen bonds in the CpG specificity of triostin A is discussed.

Anti-Bacterial Agents↗

PubMed1994

Sequence specificity of quinoxaline antibiotics. 2. NMR studies of the binding of [N-MeCys3,N-MeCys7]TANDEM and triostin A to DNA containing a CpI step.

The binding of CysMeTANDEM and triostin A to DNA containing a CpI step has been studied by one- and two-dimensional 1H NMR spectroscopy. CysMeTANDEM binds sequence specifically to CpI steps as well as TpA steps as a bis-intercalator with the peptide backbone in the minor groove of the DNA. Only nonspecific, nonintercalative binding is observed between triostin A and DNA containing a CpI step. Comparison of the CysMeTANDEM-[d(GGACITCC)]2 complex to the CysMeTANDEM-[d(GGA-TATCC)]2 complex indicates that the structures of both complexes are very similar. However, CysMeTANDEM binds less tightly to [d(GGACITCC)]2 than to [d(GGATATCC)]2. The NMR evidence presented provides molecular insight into the role of stacking interactions and hydrogen bonding between the drug and the DNA in the sequence-specific binding of CysMeTANDEM to TpA sites and of triostin A to CpG sites.

Anti-Bacterial Agents↗

PubMed1993

Solution structure of a complex between [N-MeCys3,N-MeCys7]TANDEM and [d(GATATC)]2.

[N-MeCys3,N-MeCys7]TANDEM (CysMeTANDEM) is an octadepsipeptide quinoxaline antibiotic that binds specifically by bisintercalation to double-stranded DNA at NTAN sites [Addess, K. J., Gilbert, D. E., Olsen, R. K., & Feigon, J. (1992) Biochemistry 31, 339-350; Addess, K. J., Gilbert, D. E., & Feigon, J. (1992) in Structure and Function Volume 1: Nucleic Acids (Sarma, R. H., & Sarma, M. H., Eds.) pp 147-164, Adenine Press, Schenectady, NY]. We have determined the three-dimensional structure of a complex of CysMeTANDEM and the DNA hexamer [d(GATATC)]2 using two-dimensional 1H NMR derived NOE and dihedral bond angle constraints. This is the first structure of a TpA-specific quinoxaline antibiotic in complex with DNA. Initial structures of the complex were generated by metric matrix distance geometry followed by simulated annealing. Eight of these structures, refined by restrained molecular dynamics, energy minimization, and NOE-based relaxation matrix refinement, have an average pairwise RMSD of 1.11 A for all structures, calculated using all heavy atoms of the drug and the DNA except the terminal base pairs. CysMeTANDEM binds to and affects the structure of the DNA in a manner similar to that observed in complexes of the CpG-specific quinoxaline antibiotics triostin A and echinomycin with DNA [Ughetto, G., Wang, A. H.-J., Quigley, G. J., van der Marel, G. A., van Boom, J. H., & Rich, A. (1985) Nucleic Acids Res. 13, 2305-2323; Wang, A. H.-J., Ughetto G., Quigley, G. J., Hakoshima, T., van der Marel, G. A., van Boom, J. H., & Rich, A. (1984) Science 225, 1115-1121; Wang, A. H.-J., Ughetto, G., Quigley, G. J., & Rich, A. (1986) J. Biomol. Struct. Dyn. 4, 319-342]. The two quinoxaline rings bisintercalate on either side of the two central T.A base pairs and the peptide ring lies in the minor groove. The central A.T base pairs of the complex are underwound (average helical twist angle of approximately -10 degrees) and buckle inward by approximately 20 degrees. There are intermolecular hydrogen bonds between each of the Ala NH and the AN3 protons of the TpA binding site, analogous to those observed between Ala NH and GN3 in the crystal structures of the CpG-specific complexes of echinomycin and triostin A with DNA. However, the structure of the peptide ring of CysMeTANDEM in the complex differs from that of echinomycin and triostin A.(ABSTRACT TRUNCATED AT 400 WORDS)

Amino Acid Sequence↗

PubMed1992

Proton NMR studies of [N-MeCys3,N-MeCys7]TANDEM binding to DNA oligonucleotides: sequence-specific binding at the TpA site.

[N-MeCys3,N-MeCys7]TANDEM, an undermethylated analogue of Triostin A, contains two N-methyl groups on the cysteine residues only. Footprinting results showed that [N-MeCys3,N-MeCys7]TANDEM binds strongly to DNA rich in A.T residues [Low, C. M. L., Fox, K. R., Olsen, R. K., & Waring, M. J. (1986) Nucleic Acids Res. 14, 2015-2033]. However, it was not known whether specific binding of [N-MeCys3,N-MeCys7]TANDEM requires a TpA step or an ApT step. In 1:1 saturated complexes with the octamers [d(GGATATCC)]2 and [d(GGTTAACC)]2, [N-MeCys3,N-MeCys7]TANDEM binds to each octamer as a bis-intercalator bracketing the TpA step. The octadepsipeptide ring binds in the minor groove of the DNA. Analysis of sugar coupling constants from the phase-sensitive COSY data indicates that the sugar of the thymine in the TpA binding site adopts predominantly an N-type sugar conformation, while the remaining sugars on the DNA adopt an S-type conformation, as has been observed in other Triostin A and echinomycin complexes. The drug does not bind to the octamer [d(GGAATTCC)]2 as a bis-intercalator. Only weak nonintercalative binding is observed to this DNA octamer. These results show unambiguously that [N-MeCys3,N-MeCys7]TANDEM binds sequence specifically at TpA sites in DNA. The factors underlying the sequence specificity of [N-MeCys3,N-MeCys7]TANDEM binding to DNA are discussed.

Adenine Nucleotides↗