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Mutagenic analysis of the putative abcc6 substrate-binding cavity using a new homology model

Szeri, Flóra and Corradi, Valentina and Niaziorimi, Fatemeh and Donnelly, Sylvia and Conseil, Gwenaëlle (2021) Mutagenic analysis of the putative abcc6 substrate-binding cavity using a new homology model. INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES, 22 (13). ISSN 1661-6596

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Abstract

Inactivating mutations in ABCC6 underlie the rare hereditary mineralization disorder pseudoxanthoma elasticum. ABCC6 is an ATP-binding cassette (ABC) integral membrane protein that mediates the release of ATP from hepatocytes into the bloodstream. The released ATP is extra-cellularly converted into pyrophosphate, a key mineralization inhibitor. Although ABCC6 is firmly linked to cellular ATP release, the molecular details of ABCC6-mediated ATP release remain elu-sive. Most of the currently available data support the hypothesis that ABCC6 is an ATP-dependent ATP efflux pump, an un-precedented function for an ABC transporter. This hypothesis implies the presence of an ATP-binding site in the substrate-binding cavity of ABCC6. We performed an exten-sive mutagenesis study using a new homology model based on recently published structures of its close homolog, bovine Abcc1, to characterize the substrate-binding cavity of ABCC6. Leukotriene C4 (LTC4), is a high-affinity substrate of ABCC1. We mutagenized fourteen amino acid residues in the rat ortholog of ABCC6, rAbcc6, that corresponded to the residues in ABCC1 found in the LTC4 binding cavity. Our functional characterization revealed that most of the amino acids in rAbcc6 corresponding to those found in the LTC4 binding pocket in bovine Abcc1 are not critical for ATP efflux. We conclude that the putative ATP binding site in the substrate-binding cavity of ABCC6/rAbcc6 is distinct from the bovine Abcc1 LTC4-binding site. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.

Item Type: Article
Uncontrolled Keywords: MUTAGENESIS; ABC transporter; pseudoxanthoma elasticum; Homology modeling; substrate-binding site; cellular ATP efflux;
Subjects: Q Science / természettudomány > QH Natural history / természetrajz > QH301 Biology / biológia
SWORD Depositor: MTMT SWORD
Depositing User: MTMT SWORD
Date Deposited: 28 Sep 2021 07:22
Last Modified: 28 Sep 2021 07:22
URI: http://real.mtak.hu/id/eprint/130869

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