Sandbox TMV: Difference between revisions
From Proteopedia
Jump to navigationJump to search
No edit summary |
|||
| Line 7: | Line 7: | ||
==Caspar Carboxylates== | ==Caspar Carboxylates== | ||
Two clusters of acidic amino acids are thought to be important for the disassembly of the <scene name='2tmv/2tmv_lockwasher_ring/1'>helical structure of TMV</scene>. When the virus enters cells, the higher pH and lower calcium levels increase the repulsion of neighboring carboxylates, destabilizing the capsid. This concept was originally proposed by Caspar and subsequently examined by site-directed mutagenesis <ref>Caspar carboxylates: the structural basis of tobamovirus assembly. Wang H, Planchart A, Stubbs G. Biophys. J. 1998, 74, 633-638.</ref>. Several carboxylates were identified including <scene name='2tmv/2tmv_carbox1/2'>Glu50 and ASP77</scene>, which contact each other in the helical stack (look closely at the <scene name='2tmv/2tmv_carbox1_closeup/1'>two subunits that overlap</scene> in this lockwasher complex), and a cluster of four acidic amino acids, <scene name='2tmv/2tmv_carbox2/2'>GLU95, GLU97, GLU106 and GLU109</scene>, near the center of the ring. | Two clusters of acidic amino acids are thought to be important for the disassembly of the <scene name='2tmv/2tmv_lockwasher_ring/1'>helical structure of TMV</scene>. When the virus enters cells, the higher pH and lower calcium levels increase the repulsion of neighboring carboxylates, destabilizing the capsid. This concept was originally proposed by Caspar and subsequently examined by site-directed mutagenesis <ref>Caspar carboxylates: the structural basis of tobamovirus assembly. Wang H, Planchart A, Stubbs G. Biophys. J. 1998, 74, 633-638.</ref>. Several carboxylates were identified including <scene name='2tmv/2tmv_carbox1/2'>Glu50 and ASP77</scene>, which contact each other in the helical stack (look closely at the <scene name='2tmv/2tmv_carbox1_closeup/1'>two subunits that overlap</scene> in this lockwasher complex), and a cluster of four acidic amino acids, <scene name='2tmv/2tmv_carbox2/2'>GLU95, GLU97, GLU106 and GLU109</scene>, near the center of the ring. | ||
==Repeating Subunits== | |||
Th repeating basic unit consists of 49 subunits which cover a section of 69 Å of height in three turns of the helix (= a rise of 23 Å per turn). A single strand of RNA is placed between the protein subunits at a distance of 40 Å from the outer diameter. The figure to the right depicts one basic unit. Protein and RNA are shown in spacefill mode, RNA in white, the protein changing from red to blue along the helix. The uppermoust subunit is marked light brown. Each protein subunit covers three nucleotides of the RNA | |||
[[Image:TMV-colored.gif]] | |||
<blockquote> | <blockquote> | ||
