An in vitro set-up to study Pdr5-mediated substrate translocation

Area of Science:

• Biochemistry
• Molecular Biology
• Cell Biology

Background:

• Pdr5 is a key ABC transporter in Saccharomyces cerevisiae, crucial for the pleiotropic drug resistance (PDR) network.
• Its asymmetric nucleotide binding site makes it a model for medically relevant transporters like Candida albicans Cdr1.
• Previous in vivo and vesicle studies were limited by the inability to isolate and reconstitute active Pdr5 in synthetic membranes.

Purpose of the Study:

• To achieve functional reconstitution of Pdr5 in a native-like synthetic membrane environment.
• To investigate the transport activity and nucleotide utilization of reconstituted Pdr5.
• To characterize the kinetic parameters of Pdr5's NTPase activity.

Main Methods:

• Functional reconstitution of Pdr5 into proteoliposomes in an inside-out orientation.
• Assay of NBD lipid translocation across the proteoliposome membrane.
• Measurement of NTPase activity using various nucleotides (ATP, GTP, CTP, UTP).

Main Results:

• Reconstituted Pdr5 successfully translocated NBD lipids from the outer to the inner leaflet of proteoliposomes.
• Pdr5 demonstrated the ability to utilize various nucleotides (GTP, CTP, UTP) in addition to ATP for substrate transport.
• NTPase activity of reconstituted Pdr5 was estimated, and kinetic parameters for different nucleotides were determined.

Conclusions:

• The successful functional reconstitution of Pdr5 provides a powerful system for studying its mechanism of action.
• This reconstituted system allows for detailed analysis of Pdr5's substrate translocation and nucleotide-dependent activity.
• Findings advance understanding of asymmetric ABC transporters and their role in drug resistance.