MBB331_Week11-Fall-2011

Operon subunits of in rif rna polymerase not

Info icon This preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: n rRNA available r-proteins When bind rRNA, not their own rbind protein mRNA When no rRNA is available When unbound r-proteins accumulate and bind their own mRNAs inhibits further rmRNAs protein synthesis Not all genes in these operons Not regulated by R-protein binding regulated Examples: – in α operon, α subunit of RNA in polymerase not regulated polymerase – in rif operon, β subunits of in rif RNA polymerase not controlled by L10 r-protein but by their own autogenous regulation own α operon operon A Lewin Genes VII 2000 Oxford University Press 36 (ii) TRANSLATIONAL CONTROL: access to initiation sequences • RNA phages translation of one cistron requires translationinduced changes in preceding cistron… cistron initiation requires RNA structure changes by ribosome binding preceding cistron Lewin Genes VII 2000 Oxford University Press 37 (ii) TRANSLATIONAL CONTROL: access to initiation sequences • e.g. MS2 phage replicase gene translation is dependent on coat gene expression 38 (ii) TRANSLATIONAL CONTROL: access to initiation sequences • thiM gene encodes an enzyme required for thiaminesynthesis • 5´ end of thiM mRNA contains a riboswitch whose aptamer binds thiamine pyrophosphate (TPP) • -when TPP levels are high, the cell doesn’t want to make more thiamine and binding of TPP to riboswitch blocks Shine-Dalgarno sequence Weaver, p. 198, Chapter 7 39 (ii) TRANSLATIONAL CONTROL: access to initiation sequences • thiM gene encodes an enzyme required for thiaminesynthesis • 5´ end of thiM mRNA contains a riboswitch whose aptamer binds thiamine pyrophosphate (TPP) • when TPP levels are high, the cell doesn’t want to make more thiamine and binding of TPP to riboswitch blocks Shine-Dalgarno sequence 40 (iii) ANTISENSE RNA • Antisense RNA: complementary to mRNA forms dsRNA with target mRNA • Modes of action: – Duplex RNA sequesters site in target and prevents its function – Duplex RNA changes target mRNA conformation in another transcript region thereby indirectly affecting function – eg. (a) prevent ribosome binding (b) targeting bound mRNA for degradation (c) cause premature transcriptional termination by mimicking terminator Lewin Genes VII 2000 Oxford University Press 41 EnvZ OSMOLARITY REGULATION: TRANSLATIONAL INHIBITION TRANSLATIONAL • EnvZ • • ompF (outer memb protein F) translation controlled by envZ envZ osmoregulation: envZ osmosensor envZ activates ompR in response to high ompR osmolarity osmolarity ompR activator induces micF 174 micF base transcript - an antisense...
View Full Document

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern