Cellular retinaldehyde binding protein-different binding modes and micro-solvation patterns for high-affinity 9-cis-...

Area of Science:

• Biochemistry
• Structural Biology
• Computational Chemistry

Background:

• Cellular retinaldehyde binding protein (CRALBP) plays a crucial role in retinoid metabolism.
• Mutations in CRALBP, such as R234W, are linked to retinal dystrophies.
• Understanding retinoid-CRALBP interactions is vital for comprehending visual cycle function and disease.

Purpose of the Study:

• To investigate the binding properties of various retinoid species to CRALBP using molecular dynamics (MD) simulations.
• To analyze the structural basis of CRALBP interactions with native and mutant forms, including R234W.
• To elucidate the role of microsolvation in CRALBP's recently discovered isomerase activity.

Main Methods:

• Molecular dynamics (MD) simulations of CRALBP complexes with different retinoids (9-cis-retinal, 11-cis-retinal, 9-cis-retinol, 9,13-dicis-retinal).
• Analysis of ligand binding conformations and residual solvation patterns.
• Validation of binding geometries using ZINDO/S semiempirical calculations for optical spectra.

Main Results:

• High mobility of the retinoid polyene tail in wild-type CRALBP complexes prevents stable localization in a single conformation.
• Distinct residual solvation patterns observed for CRALBP complexes with 9-cis-retinal versus 9,13-dicis-retinal.
• MD-derived binding geometries qualitatively reproduced experimental optical spectra, confirming red-shifts.

Conclusions:

• Ligand microsolvation properties are critical determinants of CRALBP's isomerase activity.
• MD simulations provide valuable insights into the structural dynamics of retinoid binding to CRALBP.
• This study enhances understanding of CRALBP function in retinoid metabolism and its implications in retinal diseases.