Globular Proteins
From Proteopedia
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=== Five Layers === | === Five Layers === | ||
Load <scene name='Globular_Proteins/Five_layers/2'>structure</scene>. Rotate the structure and attempt to identify the five layers. | Load <scene name='Globular_Proteins/Five_layers/2'>structure</scene>. Rotate the structure and attempt to identify the five layers. | ||
| - | The five layers are <scene name='Globular_Proteins/Five_layers_identified/2'>identified</scene> in colors <font color="brown"><b>Brown</b></font> through <font color="#ff0000"><b>Red</b></font>. Display<scene name='Globular_Proteins/Five_layers_phobic/1'> hydrophobic residues</scene>; it is not as obvious as with the previous proteins, but as the structure rotates one can see that most of the spheres are in the interior between the layers. | + | The five layers are <scene name='Globular_Proteins/Five_layers_identified/2'>identified</scene> in colors <font color="brown"><b>Brown</b></font> through <font color="#ff0000"><b>Red</b></font>. Display<scene name='Globular_Proteins/Five_layers_phobic/1'> hydrophobic residues</scene>; it is not as obvious as with the previous proteins, but as the structure rotates one can see that most of the spheres are in the interior between the layers. Looking at the <scene name='Globular_Proteins/Five_layers_polar/1'>polar residues</scene>, as it rotates one can observe more spheres on the edges of the structure than were seen in the previous scene. |
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| + | === Non-stabilizing Layers === | ||
| + | Load <scene name='Globular_Proteins/Non_layers/1'>structure</scene>. Even though backbone layers can be identified in these molecular structures, the layers are not extensive enough and/or positioned well enough for the hydrophobic side chains to have significant interaction so the hydrophobic attractions do not make a major contribution to their stability. Display <scene name='Globular_Proteins/Non_layers_phobic/1'>hydrophobic residues</scene>. There are fewer hydrophobic side chains in the interior, and therefore weaker hydrophobic attraction, so the major force involved in maintaining the tertiary structure is the covalent Disulfide Bonds (yellow rods) which were not present in the examples covered above. As one would expect the <scene name='Globular_Proteins/Non_layers_polar/1'>polar side chains</scene> are plentiful on the surface of the protein. | ||
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</StructureSection> | </StructureSection> | ||
<table width='500' align='right' cellpadding='10'><tr><td bgcolor='#eeeeee'><center>'''Tertiary Structures of Examples'''<scene name='Globular_Proteins/Two_layers/2'> (Initial scene)</scene></center></td></tr></table> | <table width='500' align='right' cellpadding='10'><tr><td bgcolor='#eeeeee'><center>'''Tertiary Structures of Examples'''<scene name='Globular_Proteins/Two_layers/2'> (Initial scene)</scene></center></td></tr></table> | ||
Revision as of 00:45, 6 February 2011
Globular proteins have a molecular structure that has the appearance of a glob whose 3D structure is anywhere from a sphere to a cigar. Usually the structure of a globular protein is divided into three or four levels. The primary structure is simply the sequence of amino acids forming the peptide chain. The peptide chain is folded in a repetitive fashion, and these structures with repetitive conformations are called secondary structures. Common examples of secondary structures are α-helix and β-sheets. The tertiary structure is the overall 3D structure of a protein molecule and is produced by folding the secondary structures upon themselves, and in the process the sections of the peptide that were not involved in secondary structures form turns (tight loops) and loops. Some globular proteins have a quaternary structure, and it is formed when two or more globular protein molecules (monomer) join together and form a multimeric unit. One way of characterizing globular proteins is by the number of layers of backbones the tertiary structures contain. A convenient way of classifying globular proteins is to categorize them according to the type and arrangement of secondary structures that are present and the intramolecular forces that are produced by these arrangements. The focus of the content of this page is on the tertiary structures of globular proteins illustrating the characteristics of their different backbone layers, their different classes and the intramolecular forces maintaining the tertiary structures.
Layers of Backbone Present in the Structure
Layers of backbone in the core of the structure is a feature that many, but not all, globular proteins have. The number of layers and their location vary for different proteins, but, in all case that have layers, the hydrophobic forces between the layers play a major role in maintaining the tertiary structure.
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