KVPY SX SB Exam 2015 Question Paper

Question : 120 of 120

Marks: +1, -0

Enzyme X catalyzes hydrolysis of GTP into GDP. The GTP-bound form of X transmits a signal that leads to cell proliferation. The GDP – bound form does not transmit any such signal. Mutations in X are found in many cancers. Which of the following alterations of X are most likely to contribute to cancer?

Mutations that increase the affinity of X for GDP
Mutations that decrease the affinity of X for GTP
Mutations that decrease the rate of GTP hydrolysis
Mutations that prevent expression of enzyme X.

Validate

Solution:

GTP –X Complex

\ { ––––––▸ }

Active cell division
GDP –X Complex

\ { ––––––▸ }

No cell division
and

\GTP \ { ––– ––– –––▸ } ↖{ \Hydrolysis}↙{\X \enzyme} \GDP

Mutation cause the decrease of rate of hydrolysis of GTP. Thus GTP –X complex remain present for long time and cell division become uncontrolled

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