#activation

Gene regulation in Prokaryotes

Full activation of ara operon requires

The araBAD operon exemplifies dual positive control integrating substrate availability and catabolite status. In absence of arabinose, AraC represses by looping DNA between araO2 and araI1, occluding RNA polymerase. Arabinose binding converts AraC into an activator that occupies araI1 and araI2, contacting polymerase and inducing bending. Maximal transcription additionally needs glucose starvation signaling. Elevated cAMP binds CAP, which recognizes site upstream of araI, enhancing polymerase alpha-CTD interaction. Both arabinose and CAP-cAMP together relieve looping and stimulate initiation,

Ref: Alberts et al., Molecular Biology of the Cell, 7th ed., Chapter 7: Prokaryotic Transcription Regulation, ara Operon

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Protein-Protein Interaction

If the bait and prey interact, which component is activated?

The readout of yeast two-hybrid depends on reconstitution of a functional transcription factor at the reporter locus. Bait-DNA-binding domain fusion and prey-activation domain fusion individually cannot activate transcription. Interaction bridges them, positioning the activation domain at upstream activating sequences of reporter genes such as HIS3, ADE2, or lacZ. This triggers recruitment of Mediator and RNA polymerase II, leading to measurable transcription. Reporter activation therefore serves as indirect but powerful evidence of protein-protein association inside living yeast nuclei under

Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.

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Cell Signaling GPCR Pathways - I

Rhodopsin is a GPCR activated by

photon absorption, is consistent with established principles of cell signaling, receptor pharmacology and cellular regulation. Experimental measurements of binding parameters, genetic loss-of-function studies and pharmacological interventions all converge on the same interpretation. Related options address neighboring concepts but do not satisfy the precise criterion stated in the question.

Ref: NCERT Biology Class 11–12 Alberts et al Molecular Biology of the Cell Lodish et al, Molecular Cell Biology Cooper & Hausman, The Cell Abbas et al., Cellular and Molecular Immunology (for immunology sections)

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Cell Signaling GPCR Pathways - I

Which molecule activates CaM-Kinase II initially?

Ca2+/Calmodulin, is consistent with established principles of cell signaling, receptor pharmacology and cellular regulation. Experimental measurements of binding parameters, genetic loss-of-function studies and pharmacological interventions all converge on the same interpretation. Related options address neighboring concepts but do not satisfy the precise criterion stated in the question.

Ref: NCERT Biology Class 11–12 Alberts et al Molecular Biology of the Cell Lodish et al, Molecular Cell Biology Cooper & Hausman, The Cell Abbas et al., Cellular and Molecular Immunology (for immunology sections)

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Cell Signaling GPCR Pathways - I

Activation of Gα subunit involves exchange of

GDP to GTP, is consistent with established principles of cell signaling, receptor pharmacology and cellular regulation. Experimental measurements of binding parameters, genetic loss-of-function studies and pharmacological interventions all converge on the same interpretation. Related options address neighboring concepts but do not satisfy the precise criterion stated in the question.

Ref: NCERT Biology Class 11–12 Alberts et al Molecular Biology of the Cell Lodish et al, Molecular Cell Biology Cooper & Hausman, The Cell Abbas et al., Cellular and Molecular Immunology (for immunology sections)

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