title: Two-dimensional crystallization of a small heat shock protein HSP16.3 on lipid layer.
abstract: As a member of small heat shock proteins, HSP16.3 was identified as the major membrane-bound protein of Mycobacterium tuberculosis during stationary phase. Previous studies revealed that HSP16.3 was in a nonameric form in solution. Here, two-dimensional crystal of HSP16.3 molecules on lipid monolayer was obtained for the first time. The crystal exhibited p422 symmetry with lattice parameters a=b=90A, gamma=90 degrees. The projection map of untilted crystals showed that the basic unit of the crystal was a rod-like structure with two high-density regions. The three-dimensional map at 2.2 nm resolution revealed a rod-like structure with a dimension of 56A x 32A x 25A, similar to the dimeric forms of M. jannaschii HSP16.5 and wheat HSP16.9. Cross-linking experiments confirmed that HSP16.3 nonamers dissociated into dimers upon interaction with the positively charged lipid layer. Surface plasmon resonance measurements revealed that both electrostatic and hydrophobic forces involved in the formation of the 2D crystal on the lipid monolayer. These results provide a basis for further investigation on the unique dimeric structure of HSP16.3 and its functions in vivo.
authors.affiliation: Department of Biological Sciences and Biotechnology, State-Key Laboratory of Biomembrane, Tsinghua University, Beijing 100084, PR China.
authors.forename: Yong
authors.initials: Y
authors.lastname: Chen
authors.forename: Ying-Jie
authors.initials: YJ
authors.lastname: Lu
authors.forename: Hong-Wei
authors.initials: HW
authors.lastname: Wang
authors.forename: Shu
authors.initials: S
authors.lastname: Quan
authors.forename: Zengyi
authors.initials: Z
authors.lastname: Chang
authors.forename: Sen-Fang
authors.initials: SF
authors.lastname: Sui
mesh_terms: D000588:Amines / Q000737:chemistry; D001426:Bacterial Proteins; D018833:Chaperonins / Q000737:chemistry / Q000648:ultrastructure*; D003432:Cross-Linking Reagents; D003460:Crystallization; D018360:Crystallography, X-Ray; D019281:Dimerization; D008958:Models, Molecular; D010713:Phosphatidylcholines / Q000737:chemistry; D010743:Phospholipids / Q000737:chemistry; D020349:Surface Plasmon Resonance
chemical_list: D000588:Amines; D001426:Bacterial Proteins; D003432:Cross-Linking Reagents; C431133:Hsp16.3 protein, Mycobacterium tuberculosis; D010713:Phosphatidylcholines; D010743:Phospholipids; D018833:Chaperonins; C017251:1,2-oleoylphosphatidylcholine; C009317:stearylamine