Primary structure of a protein

Whereas the primary structure of a protein is determined by the covalently linked amino acid residues in the polypeptide backbone, secondary and higher... 

The Primary Structure of a Protein Determining the Amino Acid Sequence... 

I The primary structure of a protein is simply the amino acid sequence. 

To determine the primary structure of a protein that may contain a hundred or more amino acid units, it is necessary to... 

The primary structure of a protein is the sequence of residues in the peptide chain. Aspartame consists of phenylalanine (Phe) and aspartic acid (Asp), and so its primary structure is Phe-Asp. Three fragments of the primary structure of human hemoglobin are... 

The determination of the primary structure of a protein is a very demanding analytical task, but, thanks to automated procedures, many of these structures are now known. Any modification of the primary structure of a protein—the replacement of one amino acid residue by another—may lead to a congenital disease. Even one wrong amino acid in the chain can disrupt the normal function of the molecule (Fig. 19.18). 

The primary structure of a protein is the linear sequence of amino acids linked by peptide bonds. The structural heirarchy of proteins is as follows. 

Disulfide bridges are, of course, true covalent bonds (between the sulfurs of two cysteine side chains) and are thus considered part of the primary structure of a protein by most definitions. Experimentally they also belong there, since they can be determined as part of, or an extension of, an amino acid sequence determination. However, proteins normally can fold up correctly without or before disulfide formation, and those SS links appear to influence the structure more in the manner of secondary-structural elements, by providing local specificity and stabilization. Therefore, it seems appropriate to consider them here along with the other basic elements making up three-dimensional protein structure. 

The sequence of amino acids along the polypeptide chain defines the primary structure of a protein... 

The primary structure of a protein is its amino acid sequence. During the biosynthesis of insulin in the pancreas, a continuous peptide chain with 84 residues is first synthesized—proinsu/in (see p.160). After folding of the molecule, the three disulfide bonds are first formed, and residues 31 to 63 are then proteolytically cleaved releasing the so-called C peptide. The molecule that is left over (1) now consists of two peptide chains, the A chain (21 residues, shown in yellow) and the B chain (30 residues, orange). One of the disulfide bonds is located inside the A chain, and the two others link the two chains together. 

Primary structure of a protein is simply amino acids sequence of the peptide chain. The secondary structure is a result of the different conformations that the chain can take. The tertiary structure refers to the three dimensional shape that results from twisting, bending and folding of protein helix. The quaternary structure refers to the way in which these amino acid chains of a complex protein are associated with each other (oligomer, dimers, trimers, etc.). 

From this first synthesis of an enzyme, two general conclusions were drawn. Firstly, it is possible to begin with free amino adds and to assemble them in the laboratory to give a real protein that possesses true enzymatic activity secondly, a new and independent kind of evidence was provided for the view that the primary structure of a protein determines its tertiary structure. 

The differences in primary structure can be especially informative. Each protein has a distinctive number and sequence of amino acid residues. As we shall see in Chapter 4, the primary structure of a protein determines how it folds up into a unique three-dimensional structure, and this in turn determines the function of the protein. Primary structure is the focus of the remainder of this chapter. We first consider empirical clues that amino acid sequence and protein function are closely linked, then describe how amino acid sequence is determined finally, we outline the many uses to which this information can be put. 

The chain formed by polymerization of amino acid molecules provides the primary structure of a protein. Together with any covalent crosslinkages and other modifications, this may also be called the... 

It is a site in the primary structure of a protein which has the same amino acid at that position in all species investigated. 

Primary Structure of Proteins The primary structure of a protein is the sequence of amino acids in the peptide chain. The primary structure is immensely important, because it is the sequence of amino acids that determines the higher levels of protein structure and, consequently, the function of the protein. Small changes in the primary structure can cause a protein to be completely nonfunctional. For example, sickle cell anemia is caused by the substitution of a single amino acid in the hemoglobin chain. 

The primary structure of a protein is the sequence of its amino acids. For example, the first 10 amino acids in the cytochrome c sequence are Ala-Ser-Phe-Ser-Glu-Ala-Pro-Gly-Asn-Pro, while the first 10 amino acids in the myosin sequence are Phe-Ser-Asp-Pro-Asp-Phe-Gln-Tyr-Leu-Ala. Therefore, the primary structure is just the full sequence of amino acids in the polypeptide chain or chains. Finding the primary structure of a protein is called protein sequencing. The first protein to be sequenced was the hormone insulin. 

The analytical techniques frequently employed to determine the primary structure of a protein are listed in Table I. In general, most or all of these tests will be used for proof of structure, with a subset or streamlined versions of these techniques used to confirm identity on a lot-to-lot basis. 

Primary structure of a protein is simply amino acids sequence of the peptide chain. The secondary structure is a result of the... 

For the sake of convenience, the different aspects of protein structure have been divided into four categories primary, secondary, tertiary, and quaternary structures. When we speak of the primary structure of a protein, we are concerned with the amino acid sequence of its component polypeptide chains. A protein may have a single polypeptide chain with one N and one C terminus, or it may have two or more polypeptide chains, often termed subunits, with multiple N and C termini. Secondary structure problems address themselves to whether the polypeptide chains of a protein exhibit any sort of periodicity of structure in three dimensions that is, is the polypeptide chain simply an extended ribbon, or is it present in the form of a spring or a folded structure Secondary structure has also been referred to as conformation. Tertiary structure is concerned with the overall three-dimensional appearance of the protein for example, is the shape of the protein molecule best approximated by a sphere or by a disk Last, quaternary structure refers to the number, size, and shape of component polypeptide chains in a protein. 

One of the first tasks in elucidating the primary structure of a protein is to determine its amino acid content. To accomplish this, the protein must first be hydrolyzed to break the peptide linkages. This is generally accomplished with 6... 

The sequence of amino acids in the long chain defines the primary structure of a protein. A secondary structure is determined when several residues, linked by hydrogen bonds, conform to a given combination (e.g., the a-helix, pleated sheet, and P-turns). Tertiary structure refers to the three-dimensional folded conformation of a protein. This is the biologically active conformation (crystal structure). A quaternary structure can result when two or more individual proteins assemble into two or more polypeptide chains. Conjugated proteins are complexes of proteins with other biomolecules, such as glycoproteins (sugar-proteins). 

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