Native Mass Spectrometry Characterizes the Photosynthetic Reaction Center Complex from the Purple Bacterium...

Area of Science:

• Biochemistry
• Structural Biology
• Spectroscopy

Background:

• Native mass spectrometry (MS) is a powerful technique for analyzing protein complexes.
• Membrane-embedded protein complexes, like the reaction center (RC), are challenging to study.
• Understanding pigment-protein interactions is crucial for photosynthesis research.

Purpose of the Study:

• To investigate the near-native structure and pigment interactions of the Rhodobacter sphaeroides RC complex using native MS.
• To determine the stoichiometry and topology of the RC complex.
• To assess the utility of native MS for studying membrane-bound pigment-protein complexes.

Main Methods:

• Native mass spectrometry (MS) coupled with nano-electrospray ionization (nESI).
• Detergent-stabilized RC complexes were introduced into the mass spectrometer.
• Collisional activation was used to induce gas-phase dissociation and pigment release.

Main Results:

• Native MS successfully analyzed the detergent-stabilized RC complex.
• Collisional activation led to the gradual release of chlorophyll pigments.
• Two bacteriochlorophyll a pigments remained tightly bound to the RC protein at high collision energies, indicating strong interactions.

Conclusions:

• Native MS provides insights into the near-native structure of membrane-embedded protein complexes.
• The study demonstrates the strength of pigment-protein interactions within the RC complex.
• This work paves the way for future native MS applications on photosynthetic pigment-protein complexes.