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Journal ArticleDOI

The structure of proteins; two hydrogen-bonded helical configurations of the polypeptide chain.

TL;DR: This work has used information about interatomic distances, bond angles, and other configurational parameters to construct two reasonable hydrogen-bonded helical configurations for the polypeptide chain; it is likely that these configurations constitute an important part of the structure of both fibrous and globular proteins, as well as of syntheticpolypeptides.
Abstract: During the past fifteen years we have been attacking the problem of the structure of proteins in several ways. One of these ways is the complete and accurate determination of the crystal structure of amino acids, peptides, and other simple substances related to proteins, in order that information about interatomic distances, bond angles, and other configurational parameters might be obtained that would permit the reliable prediction of reasonable configurations for the polypeptide chain. We have now used this information to construct two reasonable hydrogen-bonded helical configurations for the polypeptide chain; we think that it is likely that these configurations constitute an important part of the structure of both fibrous and globular proteins, as well as of synthetic polypeptides. A letter announcing their discovery was published last year [1]. The problem that we have set ourselves is that of finding all hydrogen-bonded structures for a single polypeptide chain, in which the residues are equivalent (except for the differences in the side chain R). An amino acid residue (other than glycine) has no symmetry elements. The general operation of conversion of one residue of a single chain into a second residue equivalent to the first is accordingly a rotation about an axis accompanied by translation along the axis. Hence the only configurations for a chain compatible with our postulate of equivalence of the residues are helical configurations. For rotational angle 180° the helical configurations may degenerate to a simple chain with all of the principal atoms, C, C' (the carbonyl carbon), N, and O, in the same plane.
Citations
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Book ChapterDOI
TL;DR: The chapter reviews that the denaturation is a process in which the spatial arrangement of the polypeptide chains within the molecule is changed from that typical of the native protein to a more disordered arrangement.
Abstract: Publisher Summary This chapter explores that the changes that take place in the protein molecules during denaturation constitute one of the most interesting and complex classes of reactions that can be found either in nature or in the laboratory These reactions are important because of the information they can provide about the more intimate details of protein structure and function They are also significant because they challenge the chemist with a difficult area for the application of chemical principles The chapter reviews that the denaturation is a process in which the spatial arrangement of the polypeptide chains within the molecule is changed from that typical of the native protein to a more disordered arrangement The chapter also discusses the classification of protein structures: primary, secondary, and tertiary structures The primary structure is that expressed by the structural chemical formula and depends entirely on the chemical valence bonds that the classical organic chemist would write down for the protein molecule The secondary structure is the configuration of the polypeptide chain that results from the satisfaction of the hydrogen bonding potential between the peptide N-H and C=O groups The tertiary structure is the pattern according to which the secondary structures are packed together within the native protein molecule The term “denaturation” as used in this chapter is indented to include changes in both the secondary and tertiary structures

4,528 citations

Journal ArticleDOI
TL;DR: The present review aims to provide a reassessment of the factors important for folding in light of current knowledge, including contributions to the free energy of folding arising from electrostatics, hydrogen-bonding and van der Waals interactions, intrinsic propensities, and hydrophobic interactions.
Abstract: T e purpose of this review is to assess the nature and magnitudes of the dominant forces in protein folding. Since proteins are only marginally stable at room temperature,’ no type of molecular interaction is unimportant, and even small interactions can contribute significantly (positively or negatively) to stability (Alber, 1989a,b; Matthews, 1987a,b). However, the present review aims to identify only the largest forces that lead to the structural features of globular proteins: their extraordinary compactness, their core of nonpolar residues, and their considerable amounts of internal architecture. This review explores contributions to the free energy of folding arising from electrostatics (classical charge repulsions and ion pairing), hydrogen-bonding and van der Waals interactions, intrinsic propensities, and hydrophobic interactions. An earlier review by Kauzmann (1959) introduced the importance of hydrophobic interactions. His insights were particularly remarkable considering that he did not have the benefit of known protein structures, model studies, high-resolution calorimetry, mutational methods, or force-field or statistical mechanical results. The present review aims to provide a reassessment of the factors important for folding in light of current knowledge. Also considered here are the opposing forces, conformational entropy and electrostatics. The process of protein folding has been known for about 60 years. In 1902, Emil Fischer and Franz Hofmeister independently concluded that proteins were chains of covalently linked amino acids (Haschemeyer & Haschemeyer, 1973) but deeper understanding of protein structure and conformational change was hindered because of the difficulty in finding conditions for solubilization. Chick and Martin (191 1) were the first to discover the process of denaturation and to distinguish it from the process of aggregation. By 1925, the denaturation process was considered to be either hydrolysis of the peptide bond (Wu & Wu, 1925; Anson & Mirsky, 1925) or dehydration of the protein (Robertson, 1918). The view that protein denaturation was an unfolding process was

3,570 citations

Book ChapterDOI
TL;DR: This chapter investigates the anatomy and taxonomy of protein structures, based on the results of three-dimensional X-ray crystallography of globular proteins.
Abstract: Publisher Summary This chapter investigates the anatomy and taxonomy of protein structures. A protein is a polypeptide chain made up of amino acid residues linked together in a definite sequence. Amino acids are “handed,” and naturally occurring proteins contain only L-amino acids. A simple mnemonic for that purpose is the “corncrib.” The sequence of side chains determines all that is unique about a particular protein, including its biological function and its specific three-dimensional structure. The major possible routes to knowledge of three-dimensional protein structure are prediction from the amino acid sequence and analysis of spectroscopic measurements such as circular dichroism, laser Raman spectroscopy, and nuclear magnetic resonance. The analysis and discussion of protein structure is based on the results of three-dimensional X-ray crystallography of globular proteins. The basic elements of protein structures are discussed. The most useful level at which protein structures are to be categorized is the domain, as there are many cases of multiple-domain proteins in which each separate domain resembles other entire smaller proteins. The simplest type of stable protein structure consists of polypeptide backbone wrapped more or less uniformly around the outside of a single hydrophobic core. The outline of the taxonomy is also provided in the chapter.

3,201 citations


Cites background from "The structure of proteins; two hydr..."

  • ...The α-helix was first described by Pauling in 1951 (Pauling et al., 1951) as a structure predicted to be stable and favorable on the basis of the accurate geometrical parameters he had recently derived for the peptide unit from smallmolecule crystal structures....

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Book ChapterDOI
TL;DR: This chapter considers the parameters that are required for an adequate description of a polypeptide chain and the mathematical method of utilizing these parameters for calculating the coordinates of all the atoms in a suitable frame of reference so that all the interatomic distances, and bond angles, can be calculated and their consequences worked out.
Abstract: Publisher Summary This chapter deals with the recent developments regarding the description and nature of the conformation of proteins and polypeptides with special reference to the stereochemical aspects of the problem. This chapter considers the parameters that are required for an adequate description of a polypeptide chain. This chapter focuses the attention on what may be called “internal parameters”—that is, those which can be defined in terms of the relationships among atoms or units that form the building blocks of the polypeptide chains. This chapter also provides an account of the mathematical method of utilizing these parameters for calculating the coordinates of all the atoms in a suitable frame of reference, so that all the interatomic distances, and bond angles, can be calculated and their consequences worked out. This chapter observes conformations in amino acids, peptides, polypeptides, and proteins.

2,802 citations

References
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Journal ArticleDOI
TL;DR: In this article, two hydrogen-bonded spiral configurations of the polypeptide chain were constructed, with the residues all equivalent, except for variation in the side chain.
Abstract: During the past fifteen years we have been carrying on a program of determination of the detailed atomic arrangements of crystals of amino acids, peptides, and other simple substances related to proteins, in order to obtain structural information that would permit the precise prediction of reasonable configurations of proteins. We have now used this information to construct two hydrogen-bonded spiral configurations of the polypeptide chain, with the residues all equivalent, except for variation in the side chain.

211 citations

Journal ArticleDOI

186 citations

Journal ArticleDOI
01 Jun 1941-Nature
TL;DR: The normal folded configuration a, the extended configuration β, and the reversible intramolecular transformation from a-keratin (or a-myosin) to β-kerATin (or β-myOSin) is the basis of the remarkable long-range elastic properties of this group of protein fibres.
Abstract: KERATIN, the protein of mammalian hairs and related epidermal tissues, the fibrous proteins of the epidermis itself, and myosin2, the principal protein of muscle tissue, all fall into one great group of fibrous proteins that have a common molecular configuration and similar long-range elastic properties. This generalization follows from a series of X-ray and supporting investigations that hare been described among other places in NATURE1. There will perhaps be no need then to summarize them again here, beyond recalling that the structural unit of the group is a ‘grid’ consisting of long polypeptide chains cross-linked by means of their side-chains, that the main-chains of this grid are not normally in the extended configuration but are thrown into a sequence of folds transverse to the side-chains, and that when the fibres are stretched the grid is pulled out flat, only to return to its folded configuration when the tension is released. The normal folded configuration we have called a, the extended configuration β, and the reversible intramolecular transformation from a-keratin (or a-myosin) to β-keratin (or β-myosin) is the basis of the remarkable long-range elastic properties of this group of protein fibres.

75 citations