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User:Michael Roberts/BIOL115 CaM
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'''SECONDARY STRUCTURE''': This is shown more clearly by a <scene name='User:Michael_Roberts/BIOL115_CaM/Structure_plus_c/2'>ribbon diagram</scene>. The computer calculates where regions of secondary structure occur and draws them as ribbons. | '''SECONDARY STRUCTURE''': This is shown more clearly by a <scene name='User:Michael_Roberts/BIOL115_CaM/Structure_plus_c/2'>ribbon diagram</scene>. The computer calculates where regions of secondary structure occur and draws them as ribbons. | ||
The alpha-helical region is now clearly defined, and there are also regions of beta-structure. | The alpha-helical region is now clearly defined, and there are also regions of beta-structure. | ||
| + | Colour key: | ||
{{Template:ColorKey_Helix}}, | {{Template:ColorKey_Helix}}, | ||
| - | {{Template:ColorKey_Strand | + | {{Template:ColorKey_Strand}}. |
| - | + | ||
The short anti-parallel beta-sheet between the adjacent EF hand loops are observed in calmodulins from various species. | The short anti-parallel beta-sheet between the adjacent EF hand loops are observed in calmodulins from various species. | ||
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'''CO-ORDINATING ATOMS''': | '''CO-ORDINATING ATOMS''': | ||
| - | To highlight the atoms that co-ordinate the Ca2+ ion, we can now enlarge those that are close (within 2.7 Å). This shows that seven oxygen atoms form the calcium co-ordination shell. Five are contributed by the side chain carboxyl groups of Asp and Glu and a sixth by the peptide carbonyl of Gln. The seventh oxygen is provided by an associated water molecule. | + | To highlight the atoms that co-ordinate the Ca2+ ion, we can now enlarge those that are close (within 2.7 Å). This shows that <scene name='User:Michael_Roberts/BIOL115_CaM/Co-ordination/3'>seven oxygen</scene> atoms form the calcium co-ordination shell. Five are contributed by the side chain carboxyl groups of Asp and Glu and a sixth by the peptide carbonyl of Gln. The seventh oxygen is provided by an associated water molecule. |
Revision as of 11:22, 12 April 2013
Sequence and structure of EF hands
The EF hand motif is present in a many proteins and it commonly bestows the ability to bind Ca2+ ions. It was first identified in parvalbumin, a muscle protein. Here we will have a look at the Ca2+-binding protein calmodulin, which possesses four EF hands. Calmodulin and its isoform, troponinC, are important intracellular Ca2+-binding proteins.
The structure below, obtained by X-ray crystallography, represents the Ca2+-binding protein calmodulin. It has a dumbell-shaped structure with two identical lobes connected by a central alpha-helix. Each lobe comprises three a helices joined by loops. A helix-loop-helix motif forms the basis of each EF hand.
Click on the 'green links' in the text in the scrollable section below to examine this molecule in more detail.
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