View source for Transcription Termination Factor Rho

{{STRUCTURE_1pvo|  PDB=1pvo  | SIZE=400| SCENE= |right|CAPTION=E. coli transcription termination factor Rho complex wit ssRNA and ANPPNP, [[1pvo]] }}


'''Transcription termination factor Rho''' is a ring-shaped RNA-DNA '''helicase''' that induces release of transcription complexes at specific loci of bacterial genomes. Several structures of Rho in various liganded states haven been solved by X-ray crystallography by the J. M. Berger lab (Berkeley): [[1a8v]], [[1pv4]], [[1pvo]], [[1xpr]], [[1xpu]], [[2a8v]], and [[2ht1]].

The [[Asymmetric Unit|asymmetric unit]] solved as [[2ht1]] contains only two chains, so it represents only one third of the [[Biological Unit|biological unit]], which is a homo-hexamer. The scene here shows this homo-hexamer in a closed state (<scene name='Transcription_Termination_Factor_Rho/Rho1_pdb_hexamer_overview/1'>restore initial scene</scene>)<ref>File [[Image:Rho1.pdb]] derived from [[2ht1]] by symmetry operations</ref>. Note that this model has only the middle 324 amino acids in each chain, lacking the first 52 and the last 57 amino acids in each chain<ref>Missing residues can be found by aligning the PDB file's SEQRES records with the sequence of the residues assigned [[Atomic coordinate file|atomic coordinates]], as listed by the [http://bip.weizmann.ac.il/oca-bin/send-s2c?w=1&id=2HT1 S2C Server]</ref>.

In this model (<scene name='Transcription_Termination_Factor_Rho/Rho1_pdb_hexamer_overview/2'>show composition</scene>), the {{Template:ColorKey Composition Protein}} hexamer is bound to {{Template:ColorKey Composition RNA}}, and some incidental "{{Template:ColorKey Composition Solvent}}" (sulfate ions).

Here is one representation showing the same Rho hexamer in a closed state and with <scene name='Transcription_Termination_Factor_Rho/Rho_closed_1/3'>RNA fragments occupying both its primary and secondary binding sites</scene>. In this scene, the foreground RNA is colored by element
({{Template:ColorKey_Element_C}}
{{Template:ColorKey_Element_O}}
{{Template:ColorKey_Element_N}}
{{Template:ColorKey_Element_P}}). Also colored are
<font color='#00a600'>'''Lys181'''</font>,
<font color='#cc3700'>'''Lys283'''</font>,
<font color='#20603c'>'''Arg347'''</font>,
<font color='#974e94'>'''Arg353'''</font>, and (in black) '''background RNA'''.  See also [[Transcription and RNA Processing]].

==3D structures of helicase==

[[Helicase]]

==Additional Resources==
For additional information, see: [[Transcription and RNA Processing]]
<br />

==Notes==
<references />