Bilayer surface association of the pHLIP peptide promotes extensive backbone desolvation and helically-constrained structures.
Despite their presence in many aspects of biology, the study of membrane proteins lags behind that of their soluble counterparts. Improving structural analysis of membrane proteins is essential. Deep-UV resonance Raman (DUVRR) spectroscopy is an emerging technique in this area and has demonstrated sensitivity to subtle structural transitions and changes in protein environment. The pH low insertion peptide (pHLIP) has three distinct structural states: disordered in an aqueous environment, partially folded and associated with a lipid membrane, and inserted into a lipid bilayer as a transmembrane helix. While the soluble and membrane-inserted forms are well characterized, the partially folded membrane-associated state has not yet been clearly described. The amide I mode, known to be sensitive to protein environment, is the same in spectra of membrane-associated and membrane-inserted pHLIP, indicating comparable levels of backbone dehydration. The amide S mode, sensitive to helical structure, indicates less helical character in the membrane-associated form compared to the membrane-inserted state, consistent with previous findings. However, the structurally sensitive amide III region is very similar in both membrane-associated and membrane-inserted pHLIP, suggesting that the membrane-associated form has a large amount of ordered structure. Where before the membrane-associated state was thought to contain mostly unordered structure and reside in a predominantly aqueous environment, we have shown that it contains a significant amount of ordered structure and rests deeper within the lipid membrane.
Department of Chemistry, University of Missouri, Columbia, MO 65211, United States.
Mia C
MC
Brown
Department of Chemistry, University of Missouri, Columbia, MO 65211, United States.
Rauta A
RA
Yakubu
Department of Chemistry, University of Missouri, Columbia, MO 65211, United States.
Jay
J
Taylor
Department of Chemistry, University of Missouri, Columbia, MO 65211, United States.
Christopher M
CM
Halsey
Department of Chemistry, University of Missouri, Columbia, MO 65211, United States.
Jian
J
Xiong
Department of Chemistry, University of Missouri, Columbia, MO 65211, United States.
Renee D
RD
Jiji
Department of Chemistry, University of Missouri, Columbia, MO 65211, United States. Electronic address: cooleyjw@missouri.edu.
Jason W
JW
Cooley
D008051:Lipid Bilayers / Q000737:chemistry*; D008565:Membrane Proteins / Q000737:chemistry*; D008958:Models, Molecular; D011487:Protein Conformation; D013499:Surface Properties
D008051:Lipid Bilayers; D008565:Membrane Proteins; C533201:pHLIP protein
Amide I; Deep-UV resonance Raman spectroscopy; Membrane protein; Structural transition; pHLIP