title: Designer amphiphilic short peptides enhance thermal stability of isolated photosystem-I.
abstract: Stability of membrane protein is crucial during protein purification and crystallization as well as in the fabrication of protein-based devices. Several recent studies have examined how various surfactants can stabilize membrane proteins out of their native membrane environment. However, there is still no single surfactant that can be universally employed for all membrane proteins. Because of the lack of knowledge on the interaction between surfactants and membrane proteins, the choice of a surfactant for a specific membrane protein remains purely empirical. Here we report that a group of short amphiphilic peptides improve the thermal stability of the multi-domain protein complex photosystem-I (PS-I) in aqueous solution and that the peptide surfactants have obvious advantages over other commonly used alkyl chain based surfactants. Of all the short peptides studied, Ac-I(5)K(2)-CONH(2) (I(5)K(2)) showed the best stabilizing effect by enhancing the melting temperature of PS-I from 48.0 degrees C to 53.0 degrees C at concentration of 0.65 mM and extending the half life of isolated PS-I significantly. AFM experiments showed that PS-I/I(5)K(2)/Triton X-100 formed large and stable vesicles and thus provide interfacial environment mimicking that of native membranes, which may partly explain why I(5)K(2) enhanced the thermal stability of PS-I. Hydrophobic and hydrophilic group length of I(x)K(y) had an important influence on the stabilization of PS-I. Our results showed that longer hydrophobic group was more effective in stabilizing PS-I. These simple short peptides therefore exhibit significant potential for applications in membrane protein studies.
authors.affiliation: Center for Bioengineering and Biotechnology, China University of Petroleum, Qingdao, People's Republic of China.
authors.forename: Baosheng
authors.initials: B
authors.lastname: Ge
authors.forename: Feng
authors.initials: F
authors.lastname: Yang
authors.forename: Daoyong
authors.initials: D
authors.lastname: Yu
authors.forename: Shuang
authors.initials: S
authors.lastname: Liu
authors.forename: Hai
authors.initials: H
authors.lastname: Xu
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry*; D015195:Drug Design; D006358:Hot Temperature; D057927:Hydrophobic and Hydrophilic Interactions; D008567:Membranes, Artificial; D017830:Octoxynol; D010455:Peptides / Q000494:pharmacology*; D045331:Photosystem I Protein Complex / Q000737:chemistry*; D055550:Protein Stability / Q000187:drug effects; D053545:Spirulina / Q000737:chemistry; D013501:Surface-Active Agents / Q000737:chemistry
chemical_list: D001426:Bacterial Proteins; D008567:Membranes, Artificial; D010455:Peptides; D045331:Photosystem I Protein Complex; D013501:Surface-Active Agents; D017830:Octoxynol