#Question id: 876
#Unit 1. Molecules and their Interaction Relevant to Biology
Prion protein is a normal constituent of brain tissue in all mammals which of the following statements are correct regarding prion protein
a) Strains of mice lacking the gene for PrP suffer no obvious ill effect
b) Illness occurs only when the normal cellular PRP or prpc occurs in an altered confirmation called PrPsc
c) The interaction of prpsc with the prpc converts the letter to prpsc initiating a Domino effect in which more and more the brain proteins converted to the disease causing form
d) the structure of prpsc is very different with much of the structure converted to amyloid like Alpha sheet.
#Question id: 877
#Unit 1. Molecules and their Interaction Relevant to Biology
The sharp transition seen in Figure suggests that
A. Proteins can be denatured by any treatment that disrupts the weak bonds stabilizing tertiary structure, such as heating, or by chemical denaturants such as urea or guanidinium chloride.
B. A comparison of the degree of unfolding as the concentration of denaturant increases reveals a sharp transition from the folded, or native, form to the unfolded, or denatured form, suggesting that only these two conformational states are present to any significant extent.
C. A similar sharp transition is observed if denaturants are removed from unfolded proteins, allowing the proteins to fold.
D. Protein folding and unfolding is an “all or none” process that results from a cooperative transition .
#Question id: 878
#Unit 1. Molecules and their Interaction Relevant to Biology
Can a peptide bind more strongly to an unfolded than the same protein in a folded state?
#Question id: 879
#Unit 1. Molecules and their Interaction Relevant to Biology
Correct approaches to protein structure prediction-:
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i. Homology modeling |
a) Methods is the Rosetta program, formulated by David Baker. To satisfy the program’s computational needs, a volunteer network of ∼100,000 computers, known as Rosetta@home, provides the 500,000 or so hours of processing time required to generate a structure. |
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ii. Structural genomics |
b) which seeks to determine the X-ray structures of all representative domains, is aimed at expanding this predictive technique. The identification of structural homology is likely to provide clues as to a protein’s function even with imperfect structure prediction. |
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iii. Threading |
c) Is a computational technique that attempts to determine the unknown structure of a protein by ascertaining whether it is consistent with a known protein structure. It does so by placing the unknown protein’s residues along the backbone of a known protein structure and then determining whether the amino acid side chains of the unknown protein are stable in that arrangement |
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iv. Ab initio |
d) Aligns the sequence of interest with the sequence of a homologous protein or domain of known structure—compensating for amino acid substitutions, insertions, and deletions—through modeling and energy minimization calculations. |
#Question id: 880
#Unit 1. Molecules and their Interaction Relevant to Biology
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: 881
#Unit 1. Molecules and their Interaction Relevant to Biology
______and ________ are the first chaperones a newly made prokaryotic protein encounters. Subsequently, many partially folded proteins are handed off to other chaperones to complete the folding process. E. coli can tolerate the elimination of_______ or________, but not both, thereby indicating that they are functionally redundant.