title: Sulfated polymannuroguluronate inhibits Tat-induced SLK cell adhesion via a novel binding site, a KKR spatial triad.
abstract: OBJECTIVE
  Sulfated polymannuroguluronate (SPMG), a candidate anti-AIDS drug, inhibited HIV replication and interfered with HIV entry into host T lymphocytes. SPMG has high binding affinity for the transactivating factor of the HIV-1 virus (Tat) via its basic domain. However, deletion or substitution of the basic domain affected, but did not completely eliminated Tat-SPMG interactions. Here, we sought to identify other SPMG binding sites in addition to the basic domain.
  
  
  METHODS
  The potential SPMG binding sites were determined using molecular simulation and a surface plasmon resonance (SPR) based competitive inhibition assay. The effect of SPMG on Tat induced adhesion was evaluated using a cell adhesion assay.
  
  
  RESULTS
  The KKR domain, a novel high-affinity heparin binding site, was identified, which consisted of a triad of Lys12, Lys41, and Arg78. The KKR domain, spatially enclosed SPMG binding site on Tat, functions as another binding domain for SPMG. Further functional evaluation demonstrated that SPMG inhibits Tat-mediated SLK cell adhesion by directly binding to the KKR region.
  
  
  CONCLUSIONS
  The KKR domain is a novel high-affinity binding domain for SPMG. Our findings provide important new insights into the molecular mechanisms of SPMG and a potential therapeutic intervention for Tat-induced cell adhesion.
authors.affiliation: Department of Pharmacology and Glycobiology, School of Medicine and Pharmacy, Ocean University of China, Qingdao 266003, China.
authors.forename: Yan-lin
authors.initials: YL
authors.lastname: Wu
authors.forename: Jing
authors.initials: J
authors.lastname: Ai
authors.forename: Jing-ming
authors.initials: JM
authors.lastname: Zhao
authors.forename: Bing
authors.initials: B
authors.lastname: Xiong
authors.forename: Xiao-jie
authors.initials: XJ
authors.lastname: Xin
authors.forename: Mei-yu
authors.initials: MY
authors.lastname: Geng
authors.forename: Xian-liang
authors.initials: XL
authors.lastname: Xin
authors.forename: Han-dong
authors.initials: HD
authors.lastname: Jiang
mesh_terms: D019380:Anti-HIV Agents / Q000494:pharmacology*; D001665:Binding Sites; D002448:Cell Adhesion / Q000187:drug effects; D045744:Cell Line, Tumor; D006493:Heparin / Q000378:metabolism; D006801:Humans; D011134:Polysaccharides / Q000494:pharmacology*; D012514:Sarcoma, Kaposi / Q000378:metabolism* / Q000473:pathology; D020349:Surface Plasmon Resonance; D054322:tat Gene Products, Human Immunodeficiency Virus / Q000378:metabolism*
chemical_list: D019380:Anti-HIV Agents; D011134:Polysaccharides; C489185:sulfated polymannuroguluronate; D054322:tat Gene Products, Human Immunodeficiency Virus; D006493:Heparin