User:Adam Meade/Sandbox 1: Difference between revisions
Adam Meade (talk | contribs) No edit summary |
Adam Meade (talk | contribs) No edit summary |
||
| Line 1: | Line 1: | ||
'''''Iron Response Regulator (Irr)''''' | '''''Iron Response Regulator (Irr)''''' | ||
---- | ---- | ||
=Background Information= | |||
Iron is potentially toxic to cells, as in the presence of oxygen, Fenton reactions can produce reactive oxygen species that can destroy essential biomolecules. Balancing the amount of iron in the cell is important and this importance is apparent from the elaborate mechanisms cells devote to iron homeostasis. Part of this iron balancing is achieved by regulation of iron import. The genes required for ferric citrate transport in ''Rhodobacter sphaeroides'' form a cluster in the order ''fecI-fecR-fecABCDE'', encoding a specialized sigma factor and a putative anti-sigma factor that together are responsible for regulated transcription of the ferric citrate transport operon, encoding an ABC-type ferric citrate transporter. In ''Escherichia coli'', ''fecI'' transcription is regulated by Fur in response to iron availability; in ''Bradyrhizobium japonicum'', as well as ''R. sphaeroides'', which both lack Fur, ''fecI'' transcription is thought to be regulated by another iron-responsive DNA binding protein, Irr, or the iron response regulator protein, which can also be considered to be a relative to the family of Fur proteins. <ref>1) Hamza I, S. Chauhan, R. Hassett, MR O'Brian, 1998. <u>The bacterial irr protein is required for coordination of heme biosynthesis with iron availability.</u>. Journal of Biological Chemistry 34:21669-74.</ref> | Iron is potentially toxic to cells, as in the presence of oxygen, Fenton reactions can produce reactive oxygen species that can destroy essential biomolecules. Balancing the amount of iron in the cell is important and this importance is apparent from the elaborate mechanisms cells devote to iron homeostasis. Part of this iron balancing is achieved by regulation of iron import. The genes required for ferric citrate transport in ''Rhodobacter sphaeroides'' form a cluster in the order ''fecI-fecR-fecABCDE'', encoding a specialized sigma factor and a putative anti-sigma factor that together are responsible for regulated transcription of the ferric citrate transport operon, encoding an ABC-type ferric citrate transporter. In ''Escherichia coli'', ''fecI'' transcription is regulated by Fur in response to iron availability; in ''Bradyrhizobium japonicum'', as well as ''R. sphaeroides'', which both lack Fur, ''fecI'' transcription is thought to be regulated by another iron-responsive DNA binding protein, Irr, or the iron response regulator protein, which can also be considered to be a relative to the family of Fur proteins. <ref>1) Hamza I, S. Chauhan, R. Hassett, MR O'Brian, 1998. <u>The bacterial irr protein is required for coordination of heme biosynthesis with iron availability.</u>. Journal of Biological Chemistry 34:21669-74.</ref> | ||
=Irr and Other Iron-Regulating Proteins= | |||
Since there are bacteria that have to have iron level-mediating proteins present but do not have the Fur (ferric uptake regulator) protein, there must be another protein that takes its place. In the case of ''B. japonicum'', which does not have the Fur protein, the Irr protein was found to be the regulator of iron levels within the cell.<ref>2) Small, S. K., S. Puri, and M. R. O’Brian. 2009. <u>Heme-dependent metalloregulation by the iron response regulator (Irr) protein in Rhizobium and other alpha-proteobacteria</u>. Biometals 22:89-97.</ref> | Since there are bacteria that have to have iron level-mediating proteins present but do not have the Fur (ferric uptake regulator) protein, there must be another protein that takes its place. In the case of ''B. japonicum'', which does not have the Fur protein, the Irr protein was found to be the regulator of iron levels within the cell.<ref>2) Small, S. K., S. Puri, and M. R. O’Brian. 2009. <u>Heme-dependent metalloregulation by the iron response regulator (Irr) protein in Rhizobium and other alpha-proteobacteria</u>. Biometals 22:89-97.</ref> | ||
=Function of Irr= | |||
Irr behaves differently than other regulatory proteins. It functions as coordinating the heme biosynthetic pathway, which ends with the insertion of Fe<sup>2+</sup> into a protoporphyrin ring to produce protoheme. It also controls the pathway by monitoring iron availability to prevent the accumulation of toxic porphyrin precursors under iron limitation, as when iron is limiting, heme cannot be produced. <ref>2) Small, S. K., S. Puri, and M. R. O’Brian. 2009. <u>Heme-dependent metalloregulation by the iron response regulator (Irr) protein in Rhizobium and other alpha-proteobacteria</u>. Biometals 22:89-97.</ref> | Irr behaves differently than other regulatory proteins. It functions as coordinating the heme biosynthetic pathway, which ends with the insertion of Fe<sup>2+</sup> into a protoporphyrin ring to produce protoheme. It also controls the pathway by monitoring iron availability to prevent the accumulation of toxic porphyrin precursors under iron limitation, as when iron is limiting, heme cannot be produced. <ref>2) Small, S. K., S. Puri, and M. R. O’Brian. 2009. <u>Heme-dependent metalloregulation by the iron response regulator (Irr) protein in Rhizobium and other alpha-proteobacteria</u>. Biometals 22:89-97.</ref> | ||
| Line 21: | Line 18: | ||
=Chemical and Physical Properties of Irr= | |||
Molecular weight: 18338.8 Da | Molecular weight: 18338.8 Da | ||
| Line 103: | Line 99: | ||
=Evolution of Irr/Fur= | |||
Amino Acid Conservation Scores | Amino Acid Conservation Scores | ||
---- | ---- | ||
| Line 265: | Line 261: | ||
=Structure of the Proposed Irr Protein= | |||
<applet load='Irr.pdb' size='300' color='black' frame='true' align='right' caption='3D Image of proposed Irr protein'/> | |||
<scene name='User:Adam_Meade/Sandbox_1/Secondary_structure_-_irr/1'>Secondary Structure</scene> | <scene name='User:Adam_Meade/Sandbox_1/Secondary_structure_-_irr/1'>Secondary Structure</scene> | ||