Lambda repressor: Difference between revisions
Wally Novak (talk | contribs) No edit summary |
Wally Novak (talk | contribs) No edit summary |
||
| Line 1: | Line 1: | ||
[[Image:1lmb.png|left|200px]] | [[Image:1lmb.png|left|200px]] | ||
{{STRUCTURE_3bdn| PDB=3bdn | SCENE= }} | {{STRUCTURE_3bdn| PDB=3bdn | SCENE= }} | ||
== Introduction == | == Introduction == | ||
cI is a transcription inhibitor of bacteriophage Lambda. Also known as Lambda Repressor, cI is responsible for maintaining the lysogenic life cycle of phage Lambda. This is achieved when two repressor dimers bind cooperatively to adjacent operator sites on the DNA. The cooperative binding induces repression of the ''cro'' gene and simultaneous activation of the ''cI'' gene, which code for proteins Cro and cI, respectively. | cI is a transcription inhibitor of bacteriophage Lambda. Also known as Lambda Repressor, cI is responsible for maintaining the lysogenic life cycle of phage Lambda. This is achieved when two repressor dimers bind cooperatively to adjacent operator sites on the DNA. The cooperative binding induces repression of the ''cro'' gene and simultaneous activation of the ''cI'' gene, which code for proteins Cro and cI, respectively. | ||
==Structural Overview== | ==Structural Overview== | ||
The Lambda Repressor dimer is composed of two identical polypeptide chains of 236 amino acid residues each. | The Lambda Repressor dimer is composed of two identical polypeptide chains of 236 amino acid residues each. The dimer is formed mainly by interactions between the CTDs, while the NTDs interact weakly in comparison. Each chain is composed of two structurally distinct domains which are connected by a short polypeptide chain which contains a cleavage-sensitive region (CSR). The NTD is responsible for the DNA-binding character of the protein and the CTD is integral in dimerization of the chains, cooperative-binding repression, and the auto-cleavage mechanism (). The principal purpose of the CSR is to provide a region which is both susceptible and insusceptible to cleavage depending upon the conformation the dimer assumes. In addition, the CSR serves to stabilize interactions between chains in the dimer. | ||
==C-Terminal Domain (CTD)== | |||
The CTD of Lambda Repressor assumes a structural conformation similar to a knotted β-sheet and is composed of 104 amino acid resides (residues 132-236). This conformation is key in establishing the dimer-forming interaction with the CTD of the opposite chain. The CTD also facilitates the dimer-dimer interaction necessary for cooperative-binding repression. The active site of the auto-cleavage mechanism of Lambda Repressor is on the CTD. Two amino acid residues mediate the auto-cleavage activity of the repressor, Lys192 and Ser149 (). | |||
<StructureSection load='3bdn' size='350' side='left' caption='CTD of Lambda Repressor cI (PDB entry [[3bdn]])' scene=''></StructureSection> | |||
==Connecting Region== | |||
The region connecting the NTD to the CTD consists of 38 amino acid residues and contains the CSR. The CSR is a long loop (residues 106-126) and serves to stabilize the dimer through interactions with the CSR of the opposite chain. Cleavage occurs between Ala111 and Gly 112 in the CSR. <StructureSection load='3bdn' size='350' side='left' caption='CSR of Lambda Repressor cI (PDB entry [[3bdn]])' scene=''></StructureSection> | |||
==N-Terminal Domain (NTD)== | |||
<StructureSection load='3bdn' size='350' side='right' caption='NTD of Lambda Repressor cI (PDB entry [[3bdn]])' scene=''></StructureSection> | |||
==Reference== | ==Reference== | ||
<ref group="xtra">PMID:18432246</ref><references group="xtra"/> | |||
<ref group="xtra">PMID:1387915</ref><references group="xtra"/> | <ref group="xtra">PMID:1387915</ref><references group="xtra"/> | ||
Revision as of 12:57, 8 November 2012
IntroductionIntroduction
cI is a transcription inhibitor of bacteriophage Lambda. Also known as Lambda Repressor, cI is responsible for maintaining the lysogenic life cycle of phage Lambda. This is achieved when two repressor dimers bind cooperatively to adjacent operator sites on the DNA. The cooperative binding induces repression of the cro gene and simultaneous activation of the cI gene, which code for proteins Cro and cI, respectively.
Structural OverviewStructural Overview
The Lambda Repressor dimer is composed of two identical polypeptide chains of 236 amino acid residues each. The dimer is formed mainly by interactions between the CTDs, while the NTDs interact weakly in comparison. Each chain is composed of two structurally distinct domains which are connected by a short polypeptide chain which contains a cleavage-sensitive region (CSR). The NTD is responsible for the DNA-binding character of the protein and the CTD is integral in dimerization of the chains, cooperative-binding repression, and the auto-cleavage mechanism (). The principal purpose of the CSR is to provide a region which is both susceptible and insusceptible to cleavage depending upon the conformation the dimer assumes. In addition, the CSR serves to stabilize interactions between chains in the dimer.
C-Terminal Domain (CTD)C-Terminal Domain (CTD)
The CTD of Lambda Repressor assumes a structural conformation similar to a knotted β-sheet and is composed of 104 amino acid resides (residues 132-236). This conformation is key in establishing the dimer-forming interaction with the CTD of the opposite chain. The CTD also facilitates the dimer-dimer interaction necessary for cooperative-binding repression. The active site of the auto-cleavage mechanism of Lambda Repressor is on the CTD. Two amino acid residues mediate the auto-cleavage activity of the repressor, Lys192 and Ser149 ().
|
Connecting RegionConnecting Region
The region connecting the NTD to the CTD consists of 38 amino acid residues and contains the CSR. The CSR is a long loop (residues 106-126) and serves to stabilize the dimer through interactions with the CSR of the opposite chain. Cleavage occurs between Ala111 and Gly 112 in the CSR.
|
N-Terminal Domain (NTD)N-Terminal Domain (NTD)
|
ReferenceReference
- ↑ Stayrook S, Jaru-Ampornpan P, Ni J, Hochschild A, Lewis M. Crystal structure of the lambda repressor and a model for pairwise cooperative operator binding. Nature. 2008 Apr 24;452(7190):1022-5. PMID:18432246 doi:10.1038/nature06831