title: Hydrophobicity of reactive site loop of SCCA1 affects its binding to hepatitis B virus.
abstract: OBJECTIVE
  To investigate the role of SCCA2 and other SCCA1 molecules in the process of hepatitis B virus (HBV) binding to mammalian cells.
  
  
  METHODS
  SCCA1 and SCCA2 were isolated from HepG2. Binding protein (BP) genes were obtained through PCR. Recombinant baculoviruses expressing SCCA1, SCCA2, BP, and different mutants were constructed and utilized to infect mammalian cells to investigate the binding ability of infected cells to HBV.
  
  
  RESULTS
  A SCCA1 gene (A1) was isolated from HepG2, but it appeared to lack the binding ability of infected cells to HBV. Two mutants, A1-BP and BP-A1, were constructed by interchanging the carboxyl terminal of A1 and BP. Cells expressing A1-BP showed an increased virus binding capacity, but not BP-A1. Comparison of A1 sequence with the sequence of BP indicated the presence of only three amino acid changes in the carboxyl terminal, two of them were found in the reactive site loop (RSL) of SCCA1. Primary structure assay revealed that the hydrophobicity of BP and AJ515706 in this domain was strong, but A1 was relatively weak. Changing the aa349 of A1 from low hydrophobic glutamic acid to high hydrophobic valine enhanced HBV binding. In contrast, HBV binding was reduced by changing the aa349 of BP from valine to glutamic acid.
  
  
  CONCLUSIONS
  The results suggest that the hydrophobicity of RSL of SCCA1 may play an important role in HBV binding to cells.
authors.affiliation: Key Laboratory of Cell Biology and Tumor Cell Engineering of Ministry of Education, Xiamen University, Xiamen 361005, Fujian Province, China.
authors.forename: Min
authors.initials: M
authors.lastname: Chen
authors.forename: Tong
authors.initials: T
authors.lastname: Cheng
authors.forename: Chen-Yu
authors.initials: CY
authors.lastname: Xu
authors.forename: Ting
authors.initials: T
authors.lastname: Wu
authors.forename: Shan-Hai
authors.initials: SH
authors.lastname: Ou
authors.forename: Tao
authors.initials: T
authors.lastname: Zhang
authors.forename: Jun
authors.initials: J
authors.lastname: Zhang
authors.forename: Ning-Shao
authors.initials: NS
authors.lastname: Xia
mesh_terms: D000951:Antigens, Neoplasm / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D016367:Baculoviridae / Q000235:genetics; D006528:Carcinoma, Hepatocellular; D045744:Cell Line, Tumor; D006509:Hepatitis B / Q000378:metabolism* / Q000821:virology; D006515:Hepatitis B virus / Q000378:metabolism*; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D008113:Liver Neoplasms; D011485:Protein Binding; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D015843:Serpins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
chemical_list: D000951:Antigens, Neoplasm; D011994:Recombinant Proteins; D015843:Serpins; C051072:squamous cell carcinoma-related antigen