|Series||Brookhaven symposia in biology -- 17|
|Contributions||Brookhaven Symposium in Biology, (17th : 1964 : Brookhaven National Laboratory)|
|The Physical Object|
|Pagination||xvii, 256 p. :|
|Number of Pages||256|
Quaternary structure refers to the arrangement of subunits and their contacts within a protein that containing 2 or more subunits. Each subunit is a separate polypeptide chain. Multisubunit proteins are referred to as oligomers. Each subunit within an oligomer is usually assigned a Greek letter to identify it. A protein can acquire a regular secondary structure for instance α-helix, β-pleated sheet, β-turn, and coils. Protein mixtures can be fractionated by chromatography. Proteins and other charged biological polymers migrate in an electric field. Primary Structure of Proteins The amino acid sequence or primary structure of a purified protein can be determined. Polypeptide sequences can be obtained from nucleic acid Size: 2MB. In order to have quaternary structure, a protein must have multiple polypeptide subunits because the structure involves the arrangement of those subunits with respect to each other. Consider hemoglobin, the oxygen-carrying protein of our blood. It contains two identical subunits known as alpha and two other identical ones known as beta.
Many protein molecules are composed of more than one subunit, where each subunit is a separate polypeptide chain and can form a stable folded structure by itself. The amino acid sequences can either be identical for each subunit (as in tobacco mosaic virus protein), or similar (as in the α and β chains of hemoglobin), or completely different. Proteins are composed of amino acid subunits that form polypeptide chains. Enzymes catalyze biochemical reactions by speeding up chemical reactions, and can either break down their substrate or build larger molecules from their substrate. The shape of an enzyme’s active site matches the shape of the substrate. Protein Mutations. Single nucleotide changes can result in amino acid substitutions. Single amino acid substitutions can result in alterations in: Protein 3D structure. Molecular Weight. Isoelectric Point. Proteolysis by specific enzymes. Molecular weights of proteolytic fragments. Problem: The structure that organizes the protein subunits of the mitotic spindle is the: a. Centromere b. Kinetochore c. Centrosome d. Cytoskeleton e. Microfilaments FREE .
Hemoglobin, for example, has a quaternary structure of four globular protein subunits: two α and two β polypeptides, each one containing an iron-based heme (Figure ). Another important class of proteins is the conjugated proteins that have a nonprotein portion. If the conjugated protein has a carbohydrate attached, it is called a glycoprotein. If it has a lipid attached, it is called a lipoprotein. . In structural biology, a protein subunit is a single protein molecule that assembles (or " coassembles ") with other protein molecules to form a protein complex. Some naturally occurring proteins have a relatively small number of subunits and therefore described as oligomeric, for example hemoglobin or DNA polymerase. The quaternary structure of a protein is how its subunits are oriented and arranged with respect to one another. As a result, quaternary structure only applies to multi-subunit proteins; that is, proteins made from more than one polypeptide chain. Proteins made from a single polypeptide will not have a quaternary structure. The quaternary structure of a protein is how its subunits are oriented and arranged with respect to one another. As a result, quaternary structure only applies to multi-subunit proteins; that is, proteins made from more than one polypeptide chain. Proteins made from a single polypeptide will not have a quaternary structure.