The classic work of Christian Anfinsen in the 1950s on the enzyme ribonuclease revealed the relation between the amino acid sequence of a protein and its conformation. Ribonuclease is a single polypeptide chain consisting of 124 amino acid residues cross-linked by four disulfide bonds. Anfinsen’s plan was to destroy the three-dimensional structure of the enzyme and to then determine what conditions were required to restore the structure.

The critical observation of Anfinsen that the denatured ribonuclease, freed of urea and b -mercaptoethanol by dialysis;

I. The sulfhydryl groups of the denatured enzyme became reduced by air, and the enzyme spontaneously refolded into a catalytically active form.

II. These experiments showed that the information needed to specify the catalytically active structure of ribonuclease is contained in its amino acid sequence.

III. The 105 wrong pairings have been picturesquely termed “scrambled” ribonuclease.

IV. He found that scrambled ribonuclease spontaneously converted into fully active, native ribonuclease when trace amounts of b -mercaptoethanol were added to an aqueous solution of the protein.

Choose incorrect options;

#Question id: 10457

#Unit 6. System Physiology – Plant

Cryptochromes are blue-light photoreceptors that mediate several blue-light responses, including__hypocotyl elongation, cotyledon expansion, petiole elongation, anthocyanin production and several other responses. Which of the following graph given below correct representing of blue light responses?

#Question id: 10458

#Unit 6. System Physiology – Plant

Which of the following statements is not true for cry proteins?

#Question id: 10459

#Unit 6. System Physiology – Plant

The role of N-terminus and the C-terminus region of the cryptochrome is given below;

a) N-terminal region is involved in the dimerization of cryptochrome and conformational changes

b) C terminus of cryptochrome forms a complex with SPA1 and COP1 that prevents them from acting, thereby preventing the degradation of HY5

c) N-terminal region of cryptochrome forms a complex with SPA1 and COP1 that prevents them from acting, thereby preventing the degradation of HY5

d) Arabidopsis plants overexpressing only the C-terminal region of cryptochrome (CCT) which resemble light-grown seedlings when grown in darkness

Which of the following combinations from the above statements is correct?

#Question id: 10460

#Unit 6. System Physiology – Plant

CCT overexpression mutant shows____

#Question id: 10461

#Unit 6. System Physiology – Plant

Model of cry1 interactions with COP1/SPA1 in the regulation of photomorphogenesis, what will happen in the dark as well as in the light in wild type condition of cryptochrome?

a) In the dark, COP1/SPA1 acts to degrade transcription factors such as HY5, which is required for photomorphogenesis

b) In the dark, cry1 is activated by phosphorylation and forms a complex with COP1 and SPA1 via the C-terminal domain, preventing them from degrading protein HY5

c) In the light, COP1/SPA1 acts to degrade transcription factors such as HY5, which is required for photomorphogenesis

d) In the light, cry1 is activated directly by blue light and indirectly by blue light induced phosphorylation and forms a complex with COP1 and SPA1 via the C-terminal domain, preventing them from degrading protein HY5

e) In light as well as in dark both case cryptochrome perfom same function such as forming a complex with COP1/ SPA1 thereby promoting an increase in HY5 protein levels and transcription

Which of the following combinations from the above statements of cryptochrome is incorrect?

#Question id: 10462

#Unit 6. System Physiology – Plant

During an experiments mutating the conserved cysteine in the LOV1 domain of phot1 does not affect phototropic responsiveness (the seedlings bend toward blue light) whereas the equivalent mutation in LOV2 abolishes the response. What will be the conclusion has been drawn from this experiments?

a)  LOV1 domain is secondarily responsible (primarily responsible is LOV2 domain) for kinase activation and LOV1 is not is coupled with the protein region Jα-helix that’s why it does not affect phototropic responsiveness

b) These studies have demonstrated that LOV2 domain is primarily responsible for kinase activation in response to blue light

c) This is due in part to the position of LOV2 within the phototropin molecule, where it is coupled to a protein region known as the Jα-helix

d) The function of LOV2 domain is thought to play a role in receptor dimerization by accomplishing the kinase activation in response to blue light

Which of the correct conclusion drawn from the above experiment?