This set of Advanced Protein Engineering Questions and Answers focuses on “New Protein Molecule Design – Phage Display”.
1. Only one cycle of directed evolution cycle is sufficient to obtain the desired protein molecule.
a) True
b) False
View Answer
Explanation: The above statement is false. Several cycles of directed evolution cycle are required to obtain the desired protein molecule. Hence, only one cycle of the directed evolution cycle is not sufficient to obtain the protein with desired characteristics.
2. The starting point of both rational and irrational protein design is a wild-type protein.
a) False
b) True
View Answer
Explanation: The above statement is true. The starting point of both rational and irrational protein design is a wild-type protein. In rational protein design,knowledge-based engineering is done, whereas in irrational protein design there is no requirement of structural and functional information.
3. Which step is performed after the mutation of genes in directed evolution?
a) X-ray crystallography
b) Protein assay
c) Protein screening
d) Expression of mutant genes
View Answer
Explanation: The step which is performed after the mutation of genes in directed evolution is the expression of mutant genes. In this step, the mutant genes which were created in the previous step are inserted into an expression vector and are expressed in a suitable host.
4. Which of the following is not a method of directed evolution?
a) Phage display
b) DNA shuffling
c) Error-prone PCR
d) Natural selection
View Answer
Explanation: Natural selection is not a method of directed evolution. Phage display, DNA shuffling, and Error-prone PCR are methods of directed evolution. Natural selection works on new sequences generated both by mutation and recombination.
5. Who pioneered phage-display technology?
a) Kary Mullis
b) Charles Chamberland
c) Robert brown
d) George Smith
View Answer
Explanation: George Smith pioneered phage-display technology in 1985. Phagedisplay is a powerful method of engineering proteins with desired binding specificities. Kary Mullis discovered PCR in 1983. Charles Chamberland invented autoclave in 1884. Robert Brown discovered the nucleus.
6. In the case of monovalent display, the valency of display depends on the ratio of phage containing phagemid vector and helper phage at the time of infection.
a) False
b) True
View Answer
Explanation: The above statement is true. In the case of monovalent display, the valency of display depends on the ratio of phage containing phagemid vector and helper phage at the time of infection. As capsid protein also comes from the helper page (during viral assembly), the infectivity of phage displaying peptide is not compromised. However, the valency of the display of peptide is decreased.
7. Which of the following bacteriophage is used in phage-display technology?
a) T4
b) λ
c) T2
d) M13
View Answer
Explanation: M13 bacteriophage is used in phage-display technology. M13 is an Escherichia coli-specific filamentous bacteriophage (a virus infecting bacteria). Gene fragments encoding polypeptides or a peptide library are fused to M13 coat protein genes.
8. M13 is a filamentous phage and it contains a circular single-stranded DNA genome.
a) False
b) True
View Answer
Explanation: The above statement is true. M13 is a filamentous phage and it contains a circular single-stranded DNA genome. The genome encodes 10 proteins, 5 of which are virion structural proteins.
9. Which of the following is the major coat protein of M13?
a) gp VI
b) gp V
c) gp IV
d) gp VIII
View Answer
Explanation: The gp VIII is the major coat protein of M13 bacteriophage. The genome of M13 is encoded in a protein coat encoded predominantly by 2700 copies of the gene protein VIII (gp VIII). gp VI, gp V, and gp IV are not major coat proteins of M13 bacteriophage.
10. Which of the following is not true for error-prone PCR?
a) It uses Taq polymerase which lacks proofreading ability
b) Occurs under imperfect PCR conditions
c) Involves annealing incompatible base-pairs to each other
d) It is not a mutagenesis method
View Answer
Explanation: Error-prone PCR uses Taq polymerase which lacks proofreading ability. It occurs under imperfect PCR conditions and it involves annealing incompatible base-pairs to each other. It is indeed a mutagenesis method. Hence, the statement “It is not a mutagenesis method” is not true for error-prone PCR.
11. Which of the following proteins are involved in initiating phage assembly and maintaining the stability of the viral particle?
a) gp III and gp VIII
b) gp VIII and gp II
c) gp VI and gp IV
d) gp VII and gp IX
View Answer
Explanation: gp VII and gp IX proteins are involved in initiating phage assembly and maintaining the stability of the viral particle. At the tail end of the phage particle, 4-5 copies of the gene VII protein (gp VII) and 4-5 copies of the gene IX protein (gp IX) are found.
12. In the case of a monovalent display, the protein fusion can be constructed in a phagemid vector that carries a copy of the viral capsid gene.
a) False
b) True
View Answer
Explanation: The above statement is true. In the case of a monovalent display, the protein fusion can be constructed in a phagemid vector that carries a copy of the viral capsid gene. In this case, the helper phages are mixed at the time of infection.
13. Which of the following is used to create a large library of mutants for a given protein gene?
a) Protein assay
b) Phage display
c) X-ray crystallography
d) Error-prone PCR
View Answer
Explanation: Error-prone PCR is used to create a large library of mutants for a given protein gene. This incorporates random mutations in the gene. Protein assay, phage display, and x-ray crystallography cannot be used to create a large library of mutants for a given protein gene.
14. In the case of polyvalent-display, all gp III are conjugated with peptide and this results in occasional loss of infectivity.
a) False
b) True
View Answer
Explanation: The above statement is true. In the case of polyvalent-display, all gp III are conjugated with peptide and this results in occasional loss of infectivity. Proteins fused to capsid proteins can be displayed in either of the two formats. i.e. polyvalent display of monovalent display.
15. In the case of a polyvalent display, the proteins can be cloned directly into a viral vector as a fusion to a capsid protein.
a) False
b) True
View Answer
Explanation: The above statement is true. In the case of a polyvalent display, the proteins can be cloned directly into a viral vector as a fusion to a capsid protein. This results in every copy of the capsid protein displaying the fusion (Polyvalency).
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