Methionine-aromatic interactions in ABCG2 influence mitoxantrone efflux

Azmir, Nur Amirah Hannan (2020) Methionine-aromatic interactions in ABCG2 influence mitoxantrone efflux. MRes thesis, University of Nottingham.

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The ATP-Binding Cassette (ABC) transporters are one of many families of membrane transport proteins that utilise the hydrolysis of ATP to provide the energy required to actively transport substrates against a concentration gradient. Some ABC transporters have been implicated in cancer multidrug resistance (MDR), where some solid tumours and blood cancers develop reduced chemosensitivity to the antineoplastic agents used to treat them due to these MDR-type ABC transporters having a very diverse substrate specificity incorporating different chemistries. One of these ABC transporters implicated in human cancer MDR is ABCG2. The mechanism behind the ability for ABCG2 to recognise a wide variety of structurally dissimilar substrates is a key question that has yet to be fully answered, with many studies trying to identify both the location of drug binding sites and the translocation pathway for allocrite recognition and efflux.

In this study, an attempt was made to understand the role of a predicted drug-binding site on the surface of ABCG2. This site is rich in methionine- aromatic interactions and it was predicted that disruption of these interac- tions would influence drug transport. Mutagenesis of 12 residues (6 methi- onines and 6 phenylalanines) was performed and mutants successfully ex- pressed and trafficked to the plasma membrane. In drug transport assays using the native substrate mitoxantrone, 3 of the 12 mutants showed a significant decrease in drug efflux compared to the wild type

From this work it was predicted that the pair of residues M541 and F545 are engaged in a methionine-aromatic interaction that is critical for drug recognition and efflux. Further future studies such as transport assays with

another native substrate and a non-native substrate can be performed to further validate this claim.

Item Type: Thesis (University of Nottingham only) (MRes)
Supervisors: Kerr, Ian D.
Layfield, Robert
Keywords: ATP-binding cassette transporters; Membrane proteins; Multidrug resistance; Mitoxantrone efflux
Subjects: Q Science > QP Physiology > QP501 Animal biochemistry
Faculties/Schools: UK Campuses > Faculty of Medicine and Health Sciences > School of Life Sciences
Item ID: 63776
Depositing User: Amirah Hannan Binti Azmir, Nur
Date Deposited: 30 Mar 2021 09:25
Last Modified: 30 Mar 2021 09:30

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