Plant Lessons: Exploring ABCB Functionality Through Structural Modeling

Aurélien Bailly,Haibing Yang,Enrico Martinoia,Markus Geisler,Angus S Murphy

doi:10.3389/fpls.2011.00108

Aurélien Bailly, Haibing Yang + Show 3 more

Open Access

https://doi.org/10.3389/fpls.2011.00108

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Abstract

In contrast to mammalian ABCB1 proteins, narrow substrate specificity has been extensively documented for plant orthologs shown to catalyze the transport of the plant hormone, auxin. Using the crystal structures of the multidrug exporters Sav1866 and MmABCB1 as templates, we have developed structural models of plant ABCB proteins with a common architecture. Comparisons of these structures identified kingdom-specific candidate substrate-binding regions within the translocation chamber formed by the transmembrane domains of ABCBs from the model plant Arabidopsis. These results suggest an early evolutionary divergence of plant and mammalian ABCBs. Validation of these models becomes a priority for efforts to elucidate ABCB function and manipulate this class of transporters to enhance plant productivity and quality.

Highlights

Members of the adenosine-5 -triphosphate (ATP)-binding cassette (ABC) transphyletic protein superfamily are predominantly transporters that function in movement of a wide variety of substrates across cellular membranes
PREDICTIONS FROM STRUCTURAL MODELING ATP-binding cassette protein subfamily B (ABCB) proteins share a common architecture ATP-binding cassette transporters share a common architecture consisting of two transmembrane domain (TMD) and two cytosolic nucleotide-binding domain (NBD)
Models derived from high-resolution crystal structures of Mus musculus ABCB1 (MmABCB1), Sav1866, and MalGFK2 are shown in Figures 1A–C

Summary

Introduction

Members of the ATP-binding cassette (ABC) transphyletic protein superfamily are predominantly transporters that function in movement of a wide variety of substrates across cellular membranes. The crystal structures of MmABCB1 and Sav1866 represent the putative ligand-binding and ligand-releasing states of the transport cycle, allowing modeling of both states in the context of the commonly accepted ABCB export mechanism (Li et al, 2010). These crystal structures are utilized by researchers to inform experimental analyses of specific

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