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G D Rose

Publications and source records attributed to G D Rose.

At least 19 recordsLinked to original sources
PubMed1999

Is protein folding hierarchic? II. Folding intermediates and transition states.

The folding reactions of some small proteins show clear evidence of a hierarchic process, whereas others, lacking detectable intermediates, do not. Evidence from folding intermediates and transition states suggests that folding begins locally, and that the formation of native secondary structure precedes the formation of tertiary interactions, not the reverse. Some notable examples in the literature have been interpreted to the contrary. For these examples, we have simulated the local structures that form when folding begins by using the LINUS program with nonlocal interactions turned off. Our results support a hierarchic model of protein folding.

Amino Acid Sequence↗
PubMed1999

Is protein folding hierarchic? I. Local structure and peptide folding.

The folding reactions of some small proteins show clear evidence of a hierarchic process, whereas others, lacking detectable intermediates, do not. Nevertheless, we argue that both classes fold hierarchically and that folding begins locally. If this is the case, then the secondary structure of a protein is determined largely by local sequence information. Experimental data and theoretical considerations support this argument. Part I of this article reviews the relationship between secondary structures in proteins and their counterparts in peptides.

Computer Simulation↗
PubMed1998

Seeking an ancient enzyme in Methanococcus jannaschii using ORF, a program based on predicted secondary structure comparisons.

We have developed a simple procedure to identify protein homologs in genomic databases. The program, called ORF, is based on comparisons of predicted secondary structure. Protein structure is far better conserved than amino acid sequence, and structure-based methods have been effective in exploiting this fact to find homologs, even among proteins with scant sequence identity. ORF is a secondary structure-based method that operates solely on predictions from sequence and requires no experimentally determined information about the structure. The approach is illustrated by an example: Thymidylate synthase, a highly conserved enzyme essential to thymidine biosynthesis in both prokaryotes and eukaryotes, is thought to be used by Archaea, but a corresponding gene has yet to be identified. Here, a candidate thymidylate synthase is identified as a previously unassigned open reading frame from the genome of Methanococcus jannaschii, viz., MJ0757. Using primary structure information alone, the optimally aligned sequence identity between MJ0757 and Escherichia coli thymidylate synthase is 7%, well below the threshold of sensitivity for detection by sequence-based methods.

Amino Acid Sequence↗
PubMed1998

Helix capping.

Helix-capping motifs are specific patterns of hydrogen bonding and hydrophobic interactions found at or near the ends of helices in both proteins and peptides. In an alpha-helix, the first four >N-H groups and last four >C=O groups necessarily lack intrahelical hydrogen bonds. Instead, such groups are often capped by alternative hydrogen bond partners. This review enlarges our earlier hypothesis (Presta LG, Rose GD. 1988. Helix signals in proteins. Science 240:1632-1641) to include hydrophobic capping. A hydrophobic interaction that straddles the helix terminus is always associated with hydrogen-bonded capping. From a global survey among proteins of known structure, seven distinct capping motifs are identified-three at the helix N-terminus and four at the C-terminus. The consensus sequence patterns of these seven motifs, together with results from simple molecular modeling, are used to formulate useful rules of thumb for helix termination. Finally, we examine the role of helix capping as a bridge linking the conformation of secondary structure to supersecondary structure.

Hydrogen Bonding↗
PubMed1997

Modeling unfolded states of proteins and peptides. II. Backbone solvent accessibility.

Buried surface area is often used as a measure of the contribution to protein folding from the hydrophobic effect. Quantitatively, the surface buried upon folding is reckoned as the difference in area between the native and unfolded states. This calculation is well defined for a known structure but model-dependent for the unfolded state. In a previous paper [Creamer, T. P., Srinivasan, R., & Rose, G. D. (1995) Biochemistry 34, 16245-16250], we developed two models that bracket the surface area of the unfolded state between limiting extremes. Using these extrema, it was shown that earlier models, such as an extended tripeptide, overestimate the surface area of side chains in the unfolded state. In this sequel to our previous paper, we focus on backbone surface in the unfolded state, again adopting the strategy of trapping the area between limiting extrema. A principal conclusion of this present study is that most backbone surface in proteins is buried within local structure.

Amino Acids↗
PubMed1995

Modeling unfolded states of peptides and proteins.

The hydrophobic effect is the major factor that drives a protein molecule toward collapse and folding. In this process, residues with apolar side chains associate to form a solvent-shielded hydrophobic core. Often, this hydrophobic contribution to folding is quantified by measuring buried apolar surface area, reckoned as the difference in area between hydrophobic groups in the folded protein and in a standard state. Typically, the standard state area of a residue is obtained from tripeptide models, with the results taken to implicitly represent values appropriate for the unfolded state. Here, we show that a tripeptide is a poor descriptor of the unfolded state, and its widespread use has prompted erroneous conclusions about folding. As an alternative, we explore two limiting models, chosen to bracket the expected behavior of the unfolded chain between reliable extremes. One extreme is represented by simulated hard-sphere peptides and shown to behave like a homopolymer with excluded volume in a good solvent. The other extreme is represented by fragments excised from folded proteins and conjectured to approximate the time-average behavior of a thermally denatured protein at Tm, the midpoint of the unfolding transition. Using these models, it is shown that the area buried by apolar side chains upon folding is considerably less than earlier estimates. For example, upon transfer from the unfolded state to the middle of an alpha-helix, an alanine side chain buries negligible area and, surprisingly, a valine side chain actually gains area. Among other applications, an improved model of the unfolded state can be used to better evaluate the driving force for helix formation in peptides and proteins.

Amino Acids↗
PubMed1995

Interactions between hydrophobic side chains within alpha-helices.

The thermodynamic basis of helix stability in peptides and proteins is a topic of considerable interest. Accordingly, we have computed the interactions between side chains of all hydrophobic residue pairs and selected triples in a model helix, using Boltzmann-weighted exhaustive modeling. Specifically, all possible pairs from the set Ala, Cys, His, Ile, Leu, Met, Phe, Trp, Tyr, and Val were modeled at spacings of (i, i + 2), (i, i + 3), and (i, i + 4) in the central turn of a model poly-alanyl alpha-helix. Significant interactions--both stabilizing and destabilizing-- were found to occur at spacings of (i, i + 3) and (i, i + 4), particularly in side chains with rings (i.e., Phe, Tyr, Trp, and His). In addition, modeling of leucine triples in a helix showed that the free energy can exceed the sum of pairwise interactions in certain cases. Our calculated interaction values both rationalize recent experimental data and provide previously unavailable estimates of the constituent energies and entropies of interaction.

Amino Acid Sequence↗
PubMed1995

LINUS: a hierarchic procedure to predict the fold of a protein.

We describe LINUS, a hierarchic procedure to predict the fold of a protein from its amino acid sequence alone. The algorithm, which has been implemented in a computer program, was applied to large, overlapping fragments from a diverse test set of 7 X-ray-elucidated proteins, with encouraging results. For all proteins but one, the overall fragment topology is well predicted, including both secondary and supersecondary structure. The algorithm was also applied to a molecule of unknown conformation, groES, in which X-ray structure determination is presently ongoing. LINUS is an acronym for Local Independently Nucleated Units of Structure. The procedure ascends the folding hierarchy in discrete stages, with concomitant accretion of structure at each step. The chain is represented by simplified geometry and folds under the influence of a primitive energy function. The only accurately described energetic quantity in this work is hard sphere repulsion--the principal force involved in organizing protein conformation [Richards, F. M. Ann. Rev. Biophys. Bioeng. 6:151-176, 1977]. Among other applications, the method is a natural tool for use in the human genome initiative.

Algorithms↗
PubMed1995

Rigid domains in proteins: an algorithmic approach to their identification.

A rigid domain, defined here as a tertiary structure common to two or more different protein conformations, can be identified numerically from atomic coordinates by finding sets of residues, one in each conformation, such that the distance between any two residues within the set belonging to one conformation is the same as the distance between the two structurally equivalent residues within the set belonging to any other conformation. The distance between two residues is taken to be the distance between their respective alpha carbon atoms. With the methods of this paper we have found in the deoxy and oxy conformations of the human hemoglobin alpha 1 beta 1 dimer a rigid domain closely related to that previously identified by Baldwin and Chothia (J. Mol. Biol. 129: 175-220, 1979). We provide two algorithms, both using the difference-distance matrix, with which to search for rigid domains directly from atomic coordinates. The first finds all rigid domains in a protein but has storage and processing demands that become prohibitively large with increasing protein size. The second, although not necessarily finding every rigid domain, is computationally tractable for proteins of any size. Because of its efficiency we are able to search protein conformations recursively for groups of non-intersecting domains. Different protein conformations, when aligned by superimposing their respective domain structures, can be examined for structural differences in regions complementing a rigid domain.

Algorithms↗
PubMed1994

The T-to-R transformation in hemoglobin: a reevaluation.

The relationship between the T, R, and R2 quaternary forms of hemoglobin is examined by computational experiments. Contrary to previous suggestions, we propose that the R quaternary form may lie on the pathway from T to R2. This proposal is consistent with four independent observations. (i) Difference distance maps are used to identify those parts of the molecule that undergo conformational change upon oxygenation. The simplest interpretation of these maps brackets R between T and R2. (ii) Linear interpolation from T to R2 passes through R. (iii) The well-known "switch" region (so called because, upon transition between the T and R quaternary forms, a residue from the beta 2 subunit toggles between two stable positions within the alpha 1 subunit) progresses from T through R to R2, successively. (iv) A hitherto-undocumented feature, diagnostic of the R structure, is noted within the alpha subunit: upon transformation from T to R, the beta-turns at the amino terminal of the E and F helices flip from one turn type to another. Upon transformation from R to R2, the latter turn--a strained conformation--flips back again.

Allosteric Regulation↗
PubMed1994

Rules for alpha-helix termination by glycine.

A predictive rule for protein folding is presented that involves two recurrent glycine-based motifs that cap the carboxyl termini of alpha helices. In proteins, helices that terminated in glycine residues were found predominantly in one of these two motifs. These glycine structures had a characteristic pattern of polar and apolar residues. Visual inspection of known helical sequences was sufficient to distinguish the two motifs from each other and from internal glycines that fail to terminate helices. These glycine motifs--in which the local sequence selects between available structures--represent an example of a stereochemical rule for protein folding.

Amino Acid Sequence↗
PubMed1994

Sequence determinants of the capping box, a stabilizing motif at the N-termini of alpha-helices.

The capping box, a recurrent hydrogen bonded motif at the N-termini of alpha-helices, caps 2 of the initial 4 backbone amide hydrogen donors of the helix (Harper ET, Rose GD, 1993, Biochemistry 32:7605-7609). In detail, the side chain of the first helical residue forms a hydrogen bond with the backbone of the fourth helical residue and, reciprocally, the side chain of the fourth residue forms a hydrogen bond with the backbone of the first residue. We now enlarge the earlier definition of this motif to include an accompanying hydrophobic interaction between residues that bracket the capping box sequence on either side. The expanded box motif--in which 2 hydrogen bonds and a hydrophobic interaction are localized within 6 consecutive residues--resembles a glycine-based capping motif found at helix C-termini (Aurora R, Srinivasan R, Rose GD, 1994, Science 264:1126-1130).

Amino Acid Sequence↗
PubMed1994

Alpha-helix-forming propensities in peptides and proteins.

Much effort has been invested in seeking to understand the thermodynamic basis of helix stability in both peptides and proteins. Recently, several groups have measured the helix-forming propensities of individual residues (Lyu, P.C., Liff, M.I., Marky, L.A., Kallenbach, N.R. Science 250:669-673, 1990; O'Neil, K.T., DeGrado, W.F. Science 250:646-651, 1990; Padmanabhan, S., Marqusee, S., Ridgeway, T., Laue, T.M., Baldwin, R.L. Nature (London) 344:268-270, 1990). Using Monte Carlo computer simulations, we tested the hypothesis that these differences in measured helix-forming propensity are due primarily to loss of side chain conformational entropy upon helix formation (Creamer, T.P., Rose, G.D. Proc. Natl. Acad. Sci. U.S.A. 89:5937-5941, 1992). Our previous study employed a rigid helix backbone, which is here generalized to a completely flexible helix model in order to ensure that earlier results were not a methodological artifact. Using this flexible model, side chain rotamer distributions and entropy losses are calculated and shown to agree with those obtained earlier. We note that the side chain conformational entropy calculated for Trp in our previous study was in error; a corrected value is presented. Extending earlier work, calculated entropy losses are found to correlate strongly with recent helix propensity scales derived from substitutions made within protein helices (Horovitz, A., Matthews, J.M., Fersht, A.R. J. Mol. Biol. 227:560-568, 1992; Blaber, M., Zhang, X.-J., Matthews, B.M. Science 260:1637-1640, 1993). In contrast, little correlation is found between these helix propensity scales and the accessible surface area buried upon formation of a model polyalanyl alpha-helix. Taken in sum, our results indicate that loss of side chain entropy is a major determinant of the helix-forming tendency of residues in both peptide and protein helices.

Computer Simulation↗
PubMed1994

Vigorous, aerobic exercise versus general motor training activities: effects on maladaptive and stereotypic behaviors of adults with both autism and mental retardation.

Examined the effects of antecedent exercise conditions on maladaptive and stereotypic behaviors in 6 adults with both autism and moderate to profound mental retardation. The behaviors were observed in a controlled environment before and after 2 exercise and 1 non-exercise conditions. From the original group of 6 participants, 2 were selected subsequently to participate in aerobic exercise immediately before performing a community-integrated vocational task. Only antecedent aerobic exercise significantly reduced maladaptive and stereotypic behaviors in the controlled setting. Neither of the less vigorous antecedent conditions did. When aerobic exercise preceded the vocational task, similar reductions were observed. There were individual differences in response to antecedent exercise. Use of antecedent aerobic exercise to reduce maladaptive and stereotypic behaviors of adults with both autism and mental retardation is supported.

Activities of Daily Living↗