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D R Muhandiram

Publications and source records attributed to D R Muhandiram.

9 recordsLinked to original sources
PubMed1998

Solution structure of a TBP-TAF(II)230 complex: protein mimicry of the minor groove surface of the TATA box unwound by TBP.

General transcription factor TFIID consists of TATA box-binding protein (TBP) and TBP-associated factors (TAF(II)s), which together play a central role in both positive and negative regulation of transcription. The N-terminal region of the 230 kDa Drosophila TAF(II) (dTAF(II)230) binds directly to TBP and inhibits TBP binding to the TATA box. We report here the solution structure of the complex formed by dTAF(II)230 N-terminal region (residues 11-77) and TBP. dTAF(II)230(11-77) comprises three alpha helices and a beta hairpin, forming a core that occupies the concave DNA-binding surface of TBP. The TBP-binding surface of dTAF(II)230 markedly resembles the minor groove surface of the partially unwound TATA box in the TBP-TATA complex. This protein mimicry of the TATA element surface provides the structural basis of the mechanism by which dTAF(II)230 negatively controls the TATA box-binding activity within the TFIID complex.

Amino Acid Sequence↗
PubMed1998

Subunit-specific backbone NMR assignments of a 64 kDa trp repressor/DNA complex: a role for N-terminal residues in tandem binding.

Deuterium decoupled, triple resonance NMR spectroscopy was used to analyze complexes of 2H, 15N, 13C labelled intact and (des2-7) trp repressor (delta 2-7 trpR) from E. coli bound in tandem to an idealized 22 basepair trp operator DNA fragment and the corepressor 5-methyltryptophan. The DNA sequence used here binds two trpR dimers in tandem resulting in chemically nonequivalent environments for the two subunits of each dimer. Sequence- and subunit-specific NMR resonance assignments were made for backbone 1HN, 15N, 13c alpha positions in both forms of the protein and for 13 C beta in the intact repressor. The differences in backbone chemical shifts between the two subunits within each dimer of delta 2-7 trpR reflect dimer-dimer contacts involving the helix-turn-helix domains and N-terminal residues consistent with a previously determined crystal structure [Lawson and Carey (1993) Nature, 366, 178-182]. Comparison of the backbone chemical shifts of DNA-bound delta 2-7 trpR with those of DNA-bound intact trpR reveals significant changes for those residues involved in N-terminal-mediated interactions observed in the crystal structure. In addition, our solution NMR data contain three sets of resonances for residues 2-12 in intact trpR suggesting that the N-terminus has multiple conformations in the tandem complex. Analysis of C alpha chemical shifts using a chemical shift index (CSI) modified for deuterium isotope effects has allowed a comparison of the secondary structure of intact and delta 2-7 tprR. Overall these data demonstrate that NMR backbone chemical shift data can be readily used to study specific structural details of large protein complexes.

Amino Acid Sequence↗
PubMed1998

Correlation between binding and dynamics at SH2 domain interfaces.

Protein recognition is a key determinant in regulating biological processes. Structures of complexes of interacting proteins provide significant insights into the mechanism of specific recognition. However, studies performed by modifying residues within a protein interface demonstrate that binding is not fully explained by these static pictures. Thus, structural data alone was not predictive of affinities in binding studies of phospholipase Cgamma1 and Syp phosphatase SH2 domains with phosphopeptides. NMR relaxation experiments probing dynamics of methyl groups of these complexes indicate a correlation between binding energy and restriction of motion at the interfacial region responsible for specific binding.

Insulin Receptor Substrate Proteins↗
PubMed1997

Pulse schemes for the measurement of 3JC'C gamma and 3JNC gamma scalar couplings in 15N,13C uniformly labeled proteins.

Pulse sequences are presented for the measurement of 3JC'C gamma and 3JNC gamma scalar couplings for all C gamma containing residues in 15N,13C uniformly labeled proteins. The methods described are based on quantitative J correlation spectroscopy pioneered by Bax and co-workers [Bax et. al. (1994) Methods Enzymol., 239, 79-105]. The combination of 3JC'C gamma and 3JNC gamma scalar coupling constants allows the assignment of discrete rotameric states about the chi 1 torsion angle in cases where such states exist or, alternatively, facilitates the establishment of noncanonical chi 1 conformations or the presence of rotameric averaging. The methods are applied to a 1.5 mM sample of staphylococcal nuclease.

Amino Acids↗
PubMed1996

Alpha helix-RNA major groove recognition in an HIV-1 rev peptide-RRE RNA complex.

The solution structure of a human immunodeficiency virus type-1 (HIV-1) Rev peptide bound to stem-loop IIB of the Rev response element (RRE) RNA was solved by nuclear magnetic resonance spectroscopy. The Rev peptide has an alpha-helical conformation and binds in the major groove of the RNA near a purine-rich internal loop. Several arginine side chains make base-specific contacts, and an asparagine residue contacts a G.A base pair. The phosphate backbone adjacent to a G.G base pair adopts an unusual structure that allows the peptide to access a widened major groove. The structure formed by the two purine-purine base pairs of the RRE creates a distinctive binding pocket that the peptide can use for specific recognition.

Amino Acid Sequence↗
PubMed1996

Structure and dynamics of a CheY-binding domain of the chemotaxis kinase CheA determined by nuclear magnetic resonance spectroscopy.

The Escherichia coli histidine autokinase CheA plays an important role in coupling signals received from membrane-bound receptors to changes in the swimming behavior of the cells in order to respond appropriately to environmental signals. Here we describe the structure of the 14 kDa fragment of the chemotaxis kinase CheA, residues 124--257, which binds to the downstream targets of phosphorylation, the response regulators CheY and CheB. This protein fragment contains the CheY-binding domain flanked on each side by regions that correspond to domain linkers in the intact protein. The structure of the domain was determined from 1429 restraints derived from heteronuclear multidimensional NMR experiments. Hybrid distance geometry--dynamical simulated annealing methods were used to calculate a family of structures that satisfy the experimental distance restraints and torsion angle restraints. The root mean square deviation of the 69 ordered residues in the domain is 0.52 A for the backbone heavy atoms and 0.99 A for all heavy atoms. The residues that have been implicated as important for CheY binding form a face consisting of several partially buried hydrophobic residues, framed by charged residues. The dynamic properties of this protein fragment were measured and analyzed using both isotropic and anisotropic models of molecular motion. The linker regions are very flexible and disordered, as evidenced by the very dynamics properties as compared to the CheY-binding domain. The CheY-binding domain of CheA is structurally similar to the histidine-containing phosphocarrier, HPr, which is a protein involved in the phosphoenolpyruvate:sugar phosphotransferase (PTS) pathway. This structural similarity suggests a possible evolutionary relationship of the PTS and chemotaxis pathways.

Amino Acid Sequence↗
PubMed1996

Correlation between dynamics and high affinity binding in an SH2 domain interaction.

Protein-protein interfaces can consist of interactions between large numbers of residues of each molecule; some of these interactions are critical in determining binding affinity and conferring specificity, while others appear to play only a marginal role. Src-homology-2 (SH2) domains bind to proteins containing phosphorylated tyrosines, with additional specificity provided by interactions with residues C-terminal to the phosphotyrosine (pTyr) residue. While the C-terminal SH2 domain of phospholipase C-gamma 1 (PLCC SH2) interacts with eight residues of a pTyr-containing peptide from its high affinity binding site on the beta-platelet-derived growth factor receptor, it can still bind tightly to a phosphopeptide containing only three residues. Novel deuterium (2H) based nuclear magnetic resonance (NMR) spin relaxation experiments which probe the nanosecond-picosecond time scale dynamics of methyl containing side chain residues have established that certain regions of the PLCC SH2 domain contacting the residues C-terminal to the pTyr have a high degree of mobility in both the free and peptide complexed states. In contrast, there is significant restriction of motion in the pTyr binding site. These results suggest a correlation between the dynamic behavior of certain groups in the PLCC SH2 complex and their contribution to high affinity binding and binding specificity.

Amino Acid Sequence↗
PubMed1995

Solution structure of a cellulose-binding domain from Cellulomonas fimi by nuclear magnetic resonance spectroscopy.

Multidimensional, multinuclear nuclear magnetic resonance spectroscopy combined with dynamical simulated annealing has been used to determine the structure of a 110 amino acid cellulose-binding domain (CBD) from Cex, a beta-1,4-glycanase from the bacterium Cellulomonas fimi (CBDcex). An experimental data set comprising 1795 interproton NOE-derived restraints, 50 phi, 34 chi 1, and 106 hydrogen bond restraints was used to calculate 20 final structures. The calculated structures have an average root-mean-square (rms) deviation about the mean structure of 0.41 A for backbone atoms and 0.67 A for all heavy atoms when fitted over the secondary structural elements. Chromatography, ultracentrifugation, and 15N NMR relaxation experiments demonstrate that CBDcex is a dimer in solution. While attempts to measure NOEs across the dimer interface were unsuccessful, a computational strategy was employed to generate dimer structures consistent with the derived data set. The results from the dimer calculations indicate that, while the monomer topologies produced in the context of the dimer can be variable, the relative positioning of secondary structural elements and side chains present in the monomer are restored upon dimer formation. CBDcex forms an extensive beta-sheet structure with a beta-barrel fold. Titration with cellohexaose, [beta-D-glucopyranosyl-(1,4)]5-D-glucose, establishes that Trp 54 and 72 participate in cellulose binding. Analysis of the structure shows that these residues are adjacent in space and exposed to solvent. Together with other proximate hydrophilic residues, these residues form a carbohydrate-binding cleft, which appears to be a feature common to all CBDs of the same family.

Actinomycetales↗