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At least 1,117 records · Page 62Linked to original sources
PubMed1998

Computer-assisted structural analysis of oligo- and polysaccharides: an extension of CASPER to multibranched structures.

The CASPER program which is used for determination of the structure of oligo- and polysaccharides has been extended. It can now handle a reduced number of experimental signals from an NMR spectrum in the comparison to the simulated spectra of structures that it generates, an improvement which is of practical importance since all signals in NMR spectra cannot always be identified. Furthermore, the program has been enhanced to simulate NMR spectra of multibranched oligo- and polysaccharides. The new developments were tested on four saccharides of known structure but of different complexity and were shown to predict the correct structures.

Aeromonas↗
PubMed2002

The crystal structures of four peptide deformylases bound to the antibiotic actinonin reveal two distinct types: a platform for the structure-based design of antibacterial agents.

Bacterial peptide deformylase (PDF) belongs to a sub-family of metalloproteases that catalyse the removal of the N-terminal formyl group from newly synthesised proteins. PDF is essential in prokaryotes and conserved throughout the eubacteria. It is therefore considered an attractive target for developing new antibacterial agents. Here, we report the crystal structures of four bacterial deformylases, free or bound to the naturally occurring antibiotic actinonin, including two from the major bacterial pathogens Pseudomonas aeruginosa and Staphylococcus aureus. The overall tertiary structure is essentially conserved but shows significant differences, namely at the C terminus, which are directly related to the deformylase type (i.e. I or II) they belong to. The geometry around the catalytic metal ion exhibits a high level of similarity within the different enzymes, as does the binding mode of actinonin to the various deformylases. However, some significant structural differences are found in the vicinity of the active site, highlighting the structural and molecular requirements for the design of a deformylase inhibitor active against a broad spectrum of bacterial strains.

Amidohydrolases↗
PubMed2003

The crystal structure of R-specific alcohol dehydrogenase from Lactobacillus brevis suggests the structural basis of its metal dependency.

The crystal structure of the apo-form of an R-specific alcohol dehydrogenase from Lactobacillus brevis (LB-RADH) was solved and refined to 1.8A resolution. LB-RADH is a member of the short-chain dehydrogenase/reductase (SDR) enyzme superfamily. It is a homotetramer with 251 amino acid residues per subunit and uses NADP(H) as co-enzyme. NADPH and the substrate acetophenone were modelled into the active site. The enantiospecificity of the enzyme can be explained on the basis of the resulting hypothetical ternary complex. In contrast to most other SDR enzymes, the catalytic activity of LB-RADH depends strongly on the binding of Mg(2+). Mg(2+) removal by EDTA inactivates the enzyme completely. In the crystal structure, the Mg(2+)-binding site is well defined. The ion has a perfect octahedral coordination sphere and occupies a special position concerning crystallographic and molecular point symmetry, meaning that each RADH tetramer contains two magnesium ions. The magnesium ion is no direct catalytic cofactor. However, it is structurally coupled to the putative C-terminal hinge of the substrate-binding loop and, via an extended hydrogen bonding network, to some side-chains forming the substrate binding region. Therefore, the presented structure of apo-RADH provides plausible explanations for the metal dependence of the enzyme.

Acetophenones↗
PubMed2002

Structure-dependent metallokinetics of antidiabetic vanadyl-picolinate complexes in rats: studies on solution structure, insulinomimetic activity, and metallokinetics.

The insulinomimetic effect of vanadium is the most remarkable and important among its several biological actions. Vanadyl ion (+4 oxidation state of vanadium) and its complexes have been found to normalize the blood glucose levels of both type 1 and 2 diabetic animals. We have developed insulinomimetic vanadyl complexes having different coordination modes, emphasizing the possible usefulness of vanadyl-picolinate [VO(pa)(2)] and its related complexes with the VO(N(2)O(2)) coordination mode. In order to apply these complexes clinically in the future, the relationship between the chemical structure, insulinomimetic action, organ distribution of vanadium, and blood disposition of vanadyl species must be closely investigated. In the present investigation, we studied the blood disposition of the vanadyl-picolinate complexes in healthy rats, and tried to understand comprehensively the relationship between the structures, insulinomimetic activity, and metallokinetic parameters of the complexes, which had been recently prepared and specifically synthesized for the present study, by using an in vivo blood circulation monitoring -- electron spin resonance (BCM-ESR) method for analyzing ESR signals due to paramagnetic metal ions and complexes in the blood in real time. Metallokinetic parameters were estimated based on the blood clearance curves in terms of a two-compartment pharmacokinetic model, and vanadyl species were indicated to be distributed in peripheral tissues and gradually eliminated from the circulating blood, depending on their chemical structures. Vanadyl concentrations in the blood of rats given bis(5-iodopicolinato)oxovanadium(IV) [VO(5ipa)(2)] and bis(3-methylpicolinato)oxovanadium(IV) [VO(3mpa)(2)] with electron-withdrawing and donating groups, respectively, remained significantly higher and longer, due to their slower clearance rates from the blood, than in rats given other complexes, suggesting that the high exposure and long residence of vanadyl species bring about the high normoglyceric effect in diabetic animals. We then examined the relationship between insulinomimetic activity and metallokinetic parameters in the family of VO(pa)(2) for further development of insulinomimetic vanadyl complexes. IC(50), the 50% inhibitory concentration of the complexes on the free fatty acid release from isolated rat adipocytes treated with epinephrine, was found to be sufficiently correlated with metallokinetic parameters such as area under the concentration curve, mean residence time, total clearance, and distribution volume at steady-state. Furthermore, the in vivo antidiabetic activity of the complexes was enhanced with increasing exposure and residence of vanadyl species in the blood of animals. On the basis of these results, we concluded that in vitro insulinomimetic activity, metallokinetic character, and in vivo antidiabetic action of vanadyl-picolinate complexes are closely related to their chemical structures.

Adipocytes↗
PubMed2003

High-resolution crystal structure of Trypanosoma brucei UDP-galactose 4'-epimerase: a potential target for structure-based development of novel trypanocides.

The crystal structure of UDP-galactose 4'-epimerase from the protozoan parasite Trypanosoma brucei in complex with the cofactor NAD(+) and a fragment of the substrates, UDP, has been determined at 2.0 A resolution (1 A = 0.1 nm). This enzyme, recently proven to be essential for this pathogenic parasite, shares 33% sequence identity with the corresponding enzyme in the human host. Structural comparisons indicate that many of the protein-ligand interactions are conserved between the two enzymes. However, in the UDP-binding pocket there is a non-conservative substitution from Gly237 in the human enzyme to Cys266 in the T. brucei enzyme. Such a significant difference could be exploited by the structure-based design of selective inhibitors using the structure of the trypanosomatid enzyme as a template.

Amino Acid Sequence↗
PubMed2000

Application of (quantitative) structure-activity relationships to progestagens: from serendipity to structure-based design.

Progestagens are drugs, which are widely used in hormonal contraception and in hormone-replacement therapy. Since the natural hormone, progesterone, lacks oral activity, much effort has been devoted to finding analogues with improved oral activity and, preferably, higher potency and selectivity. A crystal structure of the hormone binding domain (HBD) region of the progesterone receptor (PR) could only be obtained recently. For more than forty years the process of designing new progestagens could therefore only be guided by the knowledge of the structure of the ligand and its corresponding in vitro/in vivo activities. While in early days chemical intuition and simple statistics (structure-activity relationship - SAR) were leading the drug design process, in later days more complex statistics and visualization tools have become routinely part of quantitative structure-activity relationship (QSAR) studies. The present review aims to provide a general overview of the strategies, efforts and achievements of synthetic and computational chemists in more than forty years of development of progestagens.

Crystallography↗
PubMed2003

Native structural propensity in cellular retinoic acid-binding protein I 64-88: the role of locally encoded structure in the folding of a beta-barrel protein.

A central question in protein folding is the relative importance of locally encoded structure and cooperative interactions among residues distant in sequence. We have been exploring this question in a predominantly beta-sheet protein, since beta-structure formation clearly relies on both local and global sequence information. We present evidence that a 24-residue peptide corresponding to two linked hairpins of cellular retinoic acid-binding protein I (CRABP I) adopts significant native structure in aqueous solution. Prior work from our laboratory showed that the two turns contained in this fragment (turns III and IV) had the highest tendency of any of the eight turns in this anti-parallel beta-barrel to fold into native turns. In addition, the primary sequence of these two turns is well conserved throughout the structural family to which CRABP I belongs, and residues in the turns and their associated hairpins participate in a network of conserved long-range interactions. We propose that the strong local-sequence biases within the chain segment comprising turns III and IV favor longer-range interactions that are crucial to the folding and native-state stability of CRABP I, and may play a similar role in related intracellular lipid-binding proteins (iLBPs).

Amino Acid Sequence↗
PubMed1999

The molecular structure of 2alpha-hydroxyneoanisatin and structure-activity relationships among convulsant sesquiterpenes of the seco-prezizaane and picrotoxane types.

The molecular structure of 2alpha-hydroxyneoanisatin, a positional isomer of the potent neurotoxin anisatin, was determined by X-ray crystallographic analysis. This compound and four further seco-prezizaane type sesquiterpene lactones previously isolated from Illicium floridanum, which represent different structural types with respect to the mode of cyclisation, did not induce anisatin/picrotoxinin-like convulsions in mice. Based on these results and literature data for other seco-prezizaanes, structural requirements for convulsant activity are discussed. Comparison of the three dimensional molecular shape and electrostatic properties of active and inactive seco-prezizaane type lactones with compounds of the picrotoxane type resulted in the identification of a common pharmacophore structure for these different skeletal classes of convulsant natural products.

Animals↗
PubMed1994

Solution structure of a peptide fragment of human alpha-lactalbumin in trifluoroethanol: a model for local structure in the molten globule.

BACKGROUND: At low pH, human alpha-lactalbumin forms a partly folded molten globule state that contains a non-native clustering of the side chains of Tyr103, Trp104 and His107. In order to understand the conformation of this region of the protein in the molten globule state, we investigated the structure of a peptide corresponding to residues 101-110 of human alpha-lactalbumin in trifluoroethanol. RESULTS: We determined the structure of the 101-110 peptide from an NMR data set of 145 nuclear Overhauser effects and nine 3JHN alpha coupling constants, using an ensemble calculation approach to take into account the possibilities of conformational averaging of the data. The backbone of residues 3-10 in the peptide adopts a series of turns, that involving residues 5-8 being the best defined, while the side chains of residues 1, 3, 4, 5, 6 and 7 form a hydrophobic cluster. CONCLUSIONS: The peptide conformation differs from that previously determined for residues 101-110 in crystal structures of native alpha-lactalbumin determined at both high and low pH, particularly in the relative orientations of the side chains. The series of turns seen in the peptide could, however, be related to the alpha-helical structure seen for residues 104-111 in crystals at high pH, and may be important in the molten globule state for bringing the peptide chain into a compact conformation where favourable interactions between the side chains can occur.

Amino Acid Sequence↗
PubMed1996

Crystal structure of the ternary complex of mouse lung carbonyl reductase at 1.8 A resolution: the structural origin of coenzyme specificity in the short-chain dehydrogenase/reductase family.

BACKGROUND: Mouse lung carbonyl reductase (MLCR) is a member of the short-chain dehydrogenase/reductase (SDR) family. Although it uses both NADPH and NADH as coenzymes, the structural basis of its strong preference for NADPH is unknown. RESULTS: The crystal structure of the ternary complex of MLCR (with NADPH and 2-propanol) has been determined at 1.8 A resolution. This is the first three-dimensional structure of a carbonyl reductase, and MLCR is the first member of the SDR family to be solved in complex with NADPH (rather than NADH). Comparison of the MLCR ternary complex with three structures reported previously for enzymes of the SDR family (all crystallized as complexes with NADH) reveals a pair of basic residues (Lys17 and Arg39) making strong electrostatic interactions with the 2'-phosphate group of NADPH. This pair of residues is well conserved among the NADPH-preferring enzymes of the SDR family, but not among the NADH-preferring enzymes. In the latter, an aspartate side chain occupies the position of the two basic side chains. The aspartate residue, which would come into unacceptably close contact with the 2'-phosphate group of the adenosine moiety of NADPH, is replaced by a threonine or alanine in the primary sequences of NADPH-preferring enzymes of the SDR family. CONCLUSIONS: The cofactor preferences exhibited by the enzymes of the SDR family are mainly determined by the electrostatic environment surrounding the 2'-hydroxyl (or phosphate) group of the adenosine ribose moiety of NADH (or NADPH). Thus, positively charged and negatively charged environments correlate with preference for NADPH and NADH respectively.

1-Propanol↗
PubMed1999

VisualiSAR: a web-based application for clustering, structure browsing, and structure-activity relationship study.

VisualiSAR is a program designed to display chemical structures, find similarities and differences between them, and highlight relationships that might exist. The program integrates cluster analysis for the grouping of structurally related compounds, modal analysis of molecular fingerprints for the sorting and highlighting of chemical features, and a Web-based interface for flexibility and ease of use. VisualiSAR has proved useful for a number of applications including the discernment of structure-activity relationships (SAR) of high-volume screening data, and general structure browsing. This article discusses the design of the tool and illustrates two applications.

Computer Simulation↗
PubMed1996

Structure-based design of peptide presentation on a viral surface: the crystal structure of a plant/animal virus chimera at 2.8 A resolution.

BACKGROUND: We employed a genetically engineered icosahedral plant virus, cowpea mosaic virus (CPMV), as an expression and presentation system to display a 14 amino acid linear antigenic epitope found in a capsid protein of human rhinovirus 14 (HRV14). RESULT: Gram quantities of the CPMV/HRV 14 chimera were made in plants and purified particles were crystallized in a form isomorphous with wild-type CPMV. The 2.8 A resolution structure of the chimera shows that the inserted loop is well ordered and that if the loop were intact, a phenylalanine residue of CPMV would be placed in a hydrophilic environment. The resultant strain may make the loop an attractive substrate for endogenous plant proteases, as roughly 80% of the inserted polypeptides are cleaved, allowing the phenylalanine to be partially buried. Altering the phenylalanine to an arginine could relieve the stress, reducing the propensity for cleavage and increasing the likelihood that the peptide will assume a structure closely similar to its structure in HRV14. CONCLUSIONS: Successful crystallization of other CPMV chimeras in forms isomorphous with the native virus suggests that this is a viable system for structure-based design of peptide presentation.

Amino Acid Sequence↗
PubMed1995

Unlike the quaternary structure transition, the tertiary structure change of the 240s loop in allosteric aspartate transcarbamylase requires active site saturation by substrate for completion.

The quaternary structural change associated with the homotropic cooperative interactions in Escherichia coli aspartate transcarbamylase (ATCase) is accompanied by various tertiary structural modifications; the most notable one involves the 240s loop formed by residues 230--245 of the catalytic chain. In order to monitor local conformational changes in this region by fluorescence spectroscopy, Tyr-240 has been replaced by a Trp residue, in a mutant enzyme, in which both naturally occurring Trp residues in positions 209 and 284 of the catalytic chains had previously been substituted by Phe residues. This F209F284W240-ATCase still displays homotropic cooperativity for aspartate and undergoes the same T to R quaternary structure change as does the wild-type enzyme. Upon binding of the bisubstrate analogue N-(phosphonoacetyl)-L-aspartate, the fluorescence emission spectrum of this mutant shows a red shift directly proportional to the fraction of catalytic sites occupied by this compound, a maximum value of 4 nm being attained when all six active sites are ligated. An identical shift is observed with the catalytic subunits of this modified enzyme, when all three active sites are occupied. In contrast, the quaternary structural change of the F209F284W240-ATCase, monitored by small-angle X-ray scattering, is complete when only four out of six catalytic sites are occupied. Thus, the 240s loop adopts its final conformation only when the neighboring active site is bound.

Allosteric Site↗
PubMed1993

Evidence for crystal environment dominating base sequence effects on DNA conformation: crystal structures of the orthorhombic and hexagonal polymorphs of the A-DNA decamer d(GCGGGCCCGC) and comparison with their isomorphous crystal structures.

We have determined the structure of the A-DNA decamer d(GCGGGCCCGC) in two crystal forms, orthorhombic and hexagonal, at 1.7- and 1.8-A resolution, respectively. In the orthorhombic form, the fifth guanine residue has nearly trans-trans conformations for the alpha-gamma backbone torsions, as in the isomorphous orthorhombic structure d(CCCGGCCGGG) [Ramakrishnan, B., & Sundaralingam, M. (1993) J. Mol. Biol. 231, 431-444]. However, in the hexagonal form, the eighth cytosine residue adopts the trans-trans conformations for the backbone alpha-gamma torsions, as in the isomorphous hexagonal structure d(ACCGGCCGGT) [Frederick, C. A., Quigley, G. J., Teng, M.-K., Coll, M., van der Marel, G. A., van Boom, J. H., Rich, A., & Wang, A. H.-J. (1989) Eur. J. Biochem. 181, 295-307]. Even though the average helix and base-pair parameters are nearly the same in the two polymorphous crystal forms having the same sequence, many of the base-dependent local helix parameters are quite different. However, in the isomorphous crystal forms, in spite of the differing base sequences, the local helix and base-pair parameters of the duplexes are nearly the same. This indicates that, in crystals, the local conformation of a DNA structure is affected severely by the crystal packing environment rather than by the base sequence.

Base Sequence↗
PubMed1992

Structural consequences of a carcinogenic alkylation lesion on DNA: effect of O6-ethylguanine on the molecular structure of the d(CGC[e6G]AATTCGCG)-netropsin complex.

Exposure of cells to alkylating agents produces DNA lesions, most of which are repaired. However some alkyl lesions persist and play a role in inducing point mutations and the subsequent carcinogenic conversion. O6-Ethylguanine (e6G) is a relatively persistent alkylation lesion caused by the exposure of DNA to N-ethyl-N-nitrosourea. We study the consequence of the e6G incorporation in DNA by X-ray crystallography. We have obtained crystals of the modified DNA dodecamer d(CGC[e6G]AATTCGCG) and the unmodified d(CGCGAATTCGCG), complexed to the minor groove binding drug netropsin. The space group of both crystals is P2(1)2(1)2(1), isomorphous to other related dodecamer DNA crystals. The structures have been solved by the molecular replacement method and refined by the constrained least-squares procedure to R-factors of approximately 16% at resolution of approximately 2.5 A. The two independent e6G-C base pairs in the DNA duplex adopt different base-pairing schemes. The e6G4-C21 base pair has a configuration similar to a normal Watson-Crick base pair, except with one three-centered hydrogen bond pair and one direct hydrogen bond between e6G4 and C21. In contrast, the e6G16-C9 base pair adopts a wobble configuration. The ethyl group is in the proximal orientation (to N7) in both base pairs. These observations enrich and support those found in the crystal structure of d(CGC[e6G]AATTCGCG), complexed to minor groove binding drugs Hoechst 33258 and Hoechst 33342 [Sriram et al. (1992) EMBO J. 11, 225-232]. We suggest that a dynamic equilibrium between these two configurations for the e6G-C base pair is likely and would present an ambiguous signal to the cellular transcription, replication, or repair mechanisms. In contrast, thymine can pair with e6G in only one way, albeit imperfect, mimicking a Watson-Crick base pair. This may be a plausible explanation of why thymine is found preferentially incorporated across the e6G during replication. In addition, we analyze the influence of the alkylation lesion on DNA and the molecular details of netropsin-DNA interaction. In the present two new netropsin complexes, the netropsin spans across five base pairs (starting halfway between C3-G22 and e6G4-C21 base pairs and ending at T8-A17 base pair) in the narrow minor groove. This is in contrast to the earlier crystal structure of netropsin complexed with another DNA dodecamer having the same AATT central core sequence, d(CGCGAATT[br5C]GCG) [Kopka et al. (1985) J. Mol. Biol. 272, 390-395]. In the latter structure, the netropsin lies between G4-br5C21 and br5C9-G16 base pairs.(ABSTRACT TRUNCATED AT 400 WORDS)

Alkylation↗
PubMed2001

High-resolution solution structure of human intestinal trefoil factor and functional insights from detailed structural comparisons with the other members of the trefoil family of mammalian cell motility factors.

The secreted proteins intestinal trefoil factor (ITF, 59 residues), pS2 (60 residues), and spasmolytic polypeptide (SP, 106 residues) form a small family of trefoil domain-containing mammalian cell motility factors, which are essential for the maintenance of all mucous-coated epithelial surfaces. We have used 1H NMR spectroscopy to determine the high-resolution structure of human ITF, which has allowed detailed structural comparisons with the other trefoil cell motility factors. The conformation of residues 10-53 of hITF is determined to high precision, but the structure of the N- and C-terrminal residues is poorly defined by the NMR data, which is probably indicative of significant mobility. The core of the trefoil domain in hITF consists of a two-stranded antiparallel beta-sheet (Cys 36 to Asp 39 and Trp 47 to Lys 50), which is capped by an irregular loop and forms a central hairpin (loop 3). The beta-sheet is preceded by a short alpha-helix (Lys 29 to Arg 34), with the majority of the remainder of the domain contained in two loops formed from His 25 to Pro 28 (loop 2) and Ala 12 to Arg 18 (loop 1), which lie on either side of the central hairpin. The region formed by the surface of loop 2, the cleft between loop 2 and loop 3, and the adjacent face of loop 3 has previously been proposed to form the functional site of trefoil domains. Detailed comparisons of the backbone conformations and surface features of the family of trefoil cell motility factors (porcine SP, pS2, and hITF) have identified significant structural and electrostatic differences in the loop 2/loop 3 regions, which suggest that each trefoil protein has a specific target or group of target molecules.

Amino Acid Sequence↗
PubMed2001

Structural basis for alpha-K toxin specificity for K+ channels revealed through the solution 1H NMR structures of two noxiustoxin-iberiotoxin chimeras.

Noxiustoxin (NxTX) and iberiotoxin (IbTX) exhibit extraordinary differences in their ability to inhibit current through the large-conductance calcium-activated potassium (maxi-K) and voltage-gated potassium (Kv1.3) channels. The three-dimensional structures of NxTX and IbTX display differences in their alpha/beta turn and in the length of the alpha-carbon backbone. To understand the role of these differences in defining specificity, we constructed two NxTX mutants, NxTX-IbTX I and NxTX-IbTX II, and solved their solution structures by 1H NMR spectroscopy. For NxTX-IbTX I, seven amino acids comprising the alpha/beta turn in NxTX are replaced with six amino acids from the corresponding alpha/beta turn in IbTX (NxTX-YGSSAGA21-27FGVDRF21-26). In addition, NxTX-IbTX II contained the S14W mutation and deletion of the N- and C-terminal residues. Both NxTX-IbTX I and NxTX-IbTX II exhibit an alpha/beta scaffold structure typical of the alpha-K channel toxins. A helix is present from residues 10 to 19 in NxTX-IbTX I and from residues 13 to 19 in NxTX-IbTX II. The beta-sheet, defined by three antiparallel strands, is one residue longer in NxTX-IbTX I relative to NxTX-IbTX II. The two toxins also differ in the structure of the alpha/beta turn with NxTX-IbTX I resembling that of IbTX and with NxTX-IbTX II resembling that of NxTX. These differences in the beta-sheet and alpha/beta turn alter the dimensions of the toxin-channel interaction surface and provide insight into how these NxTX mutations alter K+ channel specificity for the maxi-K and Kv1.3 channels.

Amino Acid Sequence↗
PubMed2001

Structure, dynamics, and thermodynamics of the structural domain of troponin C in complex with the regulatory peptide 1-40 of troponin I.

The structure of the calcium-saturated C-domain of skeletal troponin C (CTnC) in complex with a regulatory peptide comprising residues 1-40 (Rp40) of troponin I (TnI) was determined using nuclear magnetic resonance (NMR) spectroscopy. The solution structure determined by NMR is similar to the structure of the C-domain from intact TnC in complex with TnI(1)(-)(47) determined by X-ray crystallography [Vassylyev, D. G., Takeda, S., Wakatsuki, S., Maeda, K., and Maeda, Y. (1998) Proc. Natl. Acad. Sci. U.S.A. 95, 4847-4852]. Changes in the dynamic properties of CTnC.2Ca2+ induced by Rp40 binding were investigated using backbone amide (15)N NMR relaxation measurements. Analysis of NMR relaxation data allows for extraction of motional order parameters on a per residue basis, from which the contribution of changes in picosecond to nanosecond time scale motions to the conformational entropy associated with complex formation can be estimated. The results indicate that binding of Rp40 decreases backbone flexibility in CTnC, particularly at the end of the C-terminal helix. The backbone conformational entropy change (-TDeltaS) associated with binding of Rp40 to CTnC.2Ca2+ determined from (15)N relaxation data is 9.6 +/- 0.7 kcal mol(-1) at 30 degrees C. However, estimation of thermodynamic quantities using a structural approach [Lavigne, P., Bagu, J. R., Boyko, R., Willard, L., Holmes, C. F., and Sykes, B. D. (2000) Protein Sci. 9, 252-264] reveals that the change in solvation entropy upon complex formation is dominant and overcomes the thermodynamic "cost" associated with "stiffening" of the protein backbone upon Rp40 binding. Additionally, backbone amide (15)N relaxation data measured at different concentrations of CTnC.2Ca2+.Rp40 reveal that the complex dimerizes in solution. Fitting of the apparent global rotational correlation time as a function of concentration to a monomer-dimer equilibrium yields a dimerization constant of approximately 8.3 mM.

Amino Acid Sequence↗