Crystal structure of a COG4313 outer membrane channel

Area of Science:

• Structural Biology
• Microbiology
• Biochemistry

Background:

• COG4313 proteins are outer membrane channels involved in nutrient uptake.
• Previous structure-function studies were limited by a lack of structural data.
• Pput2725 from Pseudomonas putida F1 is a member of the COG4313 family with unknown function.

Purpose of the Study:

• To determine the X-ray crystal structure of Pput2725.
• To elucidate the potential function of Pput2725 based on its structure.
• To provide a structural basis for studying other COG4313 family members.

Main Methods:

• X-ray crystallography (2.3 Å resolution).
• Single channel electrophysiology.
• Liposome swelling experiments.
• Sequence alignments and analysis of conserved residues.

Main Results:

• The 2.3 Å crystal structure reveals a 12-stranded beta-barrel occluded by an N-terminal segment.
• Electrophysiology and liposome assays indicate Pput2725 is not a channel for hydrophilic molecules.
• Bound detergent molecules and potential lateral openings suggest Pput2725 mediates hydrophobic molecule uptake.

Conclusions:

• Pput2725 functions as an outer membrane channel for hydrophobic molecule uptake in Pseudomonas putida.
• The structure reveals a mechanism for hydrophobic molecule transport, possibly via a dynamic lateral opening.
• This study provides a structural foundation for understanding the function of related COG4313 channels.