EF hand: Difference between revisions
Alice Harmon (talk | contribs) No edit summary |
Alice Harmon (talk | contribs) No edit summary |
||
| (2 intermediate revisions by 2 users not shown) | |||
| Line 1: | Line 1: | ||
[[Image:EF-hand.jpg|left]] | [[Image:EF-hand.jpg|left]] | ||
EF hands are calcium-binding motifs found in hundreds of proteins. They bind calcium ions with high affinity (K<sub>d</sub>s are in the micromolar range) and selectivity, and this property allows EF hand proteins to sense changes in intracellular calcium. In unstimulated cells cellular free calcium concentrations [Ca<sup>2+</sup>]<sub>c</sub> are in the nanomolar range (~10 nM in animal cells and ~200 nM in plant cells), and EF hands are generally unoccupied by Ca<sup>2+</sup>. Upon stimulation, Ca<sup>2+</sup> enters the cytosol from either outside the cell or from internal organelles, and [Ca<sup>2+</sup>]<sub>c</sub> rises to the micromolar range. EF hands bind Ca<sup>2+</sup>, and this binding causes a conformational change that alters the activity of the protein. | '''EF hands''' are calcium-binding motifs found in hundreds of proteins. They bind calcium ions with high affinity (K<sub>d</sub>s are in the micromolar range) and selectivity, and this property allows EF hand proteins to sense changes in intracellular calcium. In unstimulated cells cellular free calcium concentrations [Ca<sup>2+</sup>]<sub>c</sub> are in the nanomolar range (~10 nM in animal cells and ~200 nM in plant cells), and EF hands are generally unoccupied by Ca<sup>2+</sup>. Upon stimulation, Ca<sup>2+</sup> enters the cytosol from either outside the cell or from internal organelles, and [Ca<sup>2+</sup>]<sub>c</sub> rises to the micromolar range. EF hands bind Ca<sup>2+</sup>, and this binding causes a conformational change that alters the activity of the protein. | ||
The name EF hand originated from the first such structure to be described, which was in the protein [[parvalbumin]]<ref>PMID:4700463</ref>. In this protein calcium is bound by a helix-loop-helix structure that is formed by the E and F helices (letters assigned to helices in the order that they occur, starting at the N-terminus). See the annotated protein sequence for carp parvalbumin here [http://www.pdb.org/pdb/explore/remediatedSequence.do?structureId=4CPV&bionumber=1]. The structure resembles a hand with the forefinger pointing in the direction of the E helix, the thumb pointing in the direction of the H helix, and the remaining fingers curled to resemble the calcium-binding loop. | The name EF hand originated from the first such structure to be described, which was in the protein [[parvalbumin]]<ref>PMID:4700463</ref>. In this protein calcium is bound by a helix-loop-helix structure that is formed by the E and F helices (letters assigned to helices in the order that they occur, starting at the N-terminus). See the annotated protein sequence for carp parvalbumin here [http://www.pdb.org/pdb/explore/remediatedSequence.do?structureId=4CPV&bionumber=1]. The structure resembles a hand with the forefinger pointing in the direction of the E helix, the thumb pointing in the direction of the H helix, and the remaining fingers curled to resemble the calcium-binding loop. | ||
| Line 26: | Line 26: | ||
{| | {| | ||
| <applet load='4cpv' size='300' frame='true' align='right' caption='4cpv - Carp parvalbumin' scene=' | | <applet name= 'left' load='4cpv' size='300' frame='true' align='right' caption='[[4cpv]] - Carp parvalbumin' scene='43/436105/Parvalbumin/4' /><Br>'''4cpv''' <Br><scene name='43/436105/Parvalbumin/4' target= 'left'>1. Holoprotein</scene><scene name='43/436105/Parvalbumin/4' target= 'left'>1. Holoprotein</scene><Br><scene name='43/436105/Parvalbumin/3' target= 'left'>2. Pair of EF hands</scene><br><scene name='43/436105/Parvalbumin/2' target= 'left'>3. The original EF-Hand</scene><br><scene name='43/436105/Parvalbumin/1' target= 'left'>4. Calcium-binding loop</scene> | ||
| <applet load='1prw' size='300' frame='true' align='right' caption='1prw - Bovine calmodulin' scene=' | | <applet name= 'middle' load='1prw' size='300' frame='true' align='right' caption='[[1prw]] - Bovine calmodulin' scene='43/436105/Calmodulin/4' /><Br>'''1prw''' <Br><scene name='43/436105/Calmodulin/4' target= 'middle'>1. Holoprotein</scene><scene name='43/436105/Calmodulin/4' target= 'middle'>1. Holoprotein</scene><Br><scene name='43/436105/Calmodulin/3' target= 'middle'>2. Pair of EF hands</scene><br><scene name='43/436105/Calmodulin/2' target= 'middle'>3. EF hand I</scene><br><scene name='43/436105/Calmodulin/1' target= 'middle'>4. Calcium-binding loop</scene> | ||
| <applet load='3HX4' size='300' frame='true' align='left' caption='3hx4 - active TgCDPK1' scene = ' | | <applet name= 'right' load='3HX4' size='300' frame='true' align='left' caption='[[3hx4]] - active TgCDPK1' scene = '43/436105/Cdpk/1' /><Br>'''3HX4'''<Br><scene name='43/436105/Cdpk/1' target= 'right'>1. Holoprotein</scene><scene name='43/436105/Cdpk/1' target= 'right'>1. Holoprotein</scene><Br><scene name='43/436105/Cdpk_ef_hand_pair/1' target= 'right'>2. Pair of EF hands</scene><br><scene name='43/436105/Cdpk_ef_iv/2' target= 'right'>3. EF hand IV</scene><br><scene name='43/436105/Cdpk_ef_iv/1' target= 'right'>4. Calcium-binding loop</scene> | ||
|} | |} | ||
=References= | =References= | ||