title: C-termini are essential and distinct for nucleic acid binding of human NABP1 and NABP2.
abstract: BACKGROUND
  Human Nucleic Acid Binding Protein 1 and 2 (hNABP1 and 2; also known as hSSB2 and 1, respectively) are two newly identified single-stranded (ss) DNA binding proteins (SSB). Both NABP1 and NABP2 have a conserved oligonucleotide/oligosaccharide-binding (OB)-fold domain and a divergent carboxy-terminal domain, the functional importance of which is unknown.
  
  
  METHODS
  Recombinant hNABP1/2 proteins were purified using affinity and size exclusion chromatography and their identities confirmed by mass spectrometry. Oligomerization state was checked by sucrose gradient centrifugation. Secondary structure was determined by circular dichroism spectroscopy. Nucleic acid binding ability was examined by EMSA and ITC.
  
  
  RESULTS
  Both hNABP1 and hNABP2 exist as monomers in solution; however, hNABP2 exhibits anomalous behavior. CD spectroscopy revealed that the C-terminus of hNABP2 is highly disordered. Deletion of the C-terminal tail diminishes the DNA binding ability and protein stability of hNABP2. Although both hNABP1 and hNABP2 prefer to bind ssDNA than double-stranded (ds) DNA, hNABP1 has a higher affinity for ssDNA than hNABP2. Unlike hNABP2, hNABP1 protein binds and multimerizes on ssDNA with the C-terminal tail responsible for its multimerization. Both hNABP1 and hNABP2 are able to bind single-stranded RNA, with hNABP2 having a higher affinity than hNABP1.
  
  
  CONCLUSIONS
  Biochemical evidence suggests that the C-terminal region of NABP1 and NABP2 is essential for their functionality and may lead to different roles in DNA and RNA metabolism.
  
  
  CONCLUSIONS
  This is the first report demonstrating the regulation and functional properties of the C-terminal domain of hNABP1/2, which might be a general characteristic of OB-fold proteins.
authors.affiliation: Department of Biochemistry, University of Saskatchewan, Health Sciences Building, 107 Wiggins Road, Saskatoon, Saskatchewan S7N 5E5, Canada.
authors.forename: Venkatasubramanian
authors.initials: V
authors.lastname: Vidhyasagar
authors.affiliation: Department of Biochemistry, University of Saskatchewan, Health Sciences Building, 107 Wiggins Road, Saskatoon, Saskatchewan S7N 5E5, Canada.
authors.forename: Yujiong
authors.initials: Y
authors.lastname: He
authors.affiliation: Department of Biochemistry, University of Saskatchewan, Health Sciences Building, 107 Wiggins Road, Saskatoon, Saskatchewan S7N 5E5, Canada.
authors.forename: Manhong
authors.initials: M
authors.lastname: Guo
authors.affiliation: Department of Biochemistry, University of Saskatchewan, Health Sciences Building, 107 Wiggins Road, Saskatoon, Saskatchewan S7N 5E5, Canada.
authors.forename: Hao
authors.initials: H
authors.lastname: Ding
authors.affiliation: Department of Biochemistry, University of Saskatchewan, Health Sciences Building, 107 Wiggins Road, Saskatoon, Saskatchewan S7N 5E5, Canada.
authors.forename: Tanu
authors.initials: T
authors.lastname: Talwar
authors.affiliation: Department of Biochemistry, University of Saskatchewan, Health Sciences Building, 107 Wiggins Road, Saskatoon, Saskatchewan S7N 5E5, Canada.
authors.forename: Vi
authors.initials: V
authors.lastname: Nguyen
authors.affiliation: Department of Biochemistry, University of Saskatchewan, Health Sciences Building, 107 Wiggins Road, Saskatoon, Saskatchewan S7N 5E5, Canada.
authors.forename: Jessica
authors.initials: J
authors.lastname: Nwosu
authors.affiliation: Department of Medicine, University of Saskatchewan, Health Sciences Building, 107 Wiggins Road, Saskatoon, Saskatchewan S7N 5E5, Canada; Canadian Centre for Health and Safety in Agriculture, University of Saskatchewan, Health Sciences Building, 107 Wiggins Road, Saskatoon, Saskatchewan S7N 5E5, Canada.
authors.forename: George
authors.initials: G
authors.lastname: Katselis
authors.affiliation: Department of Biochemistry, University of Saskatchewan, Health Sciences Building, 107 Wiggins Road, Saskatoon, Saskatchewan S7N 5E5, Canada. Electronic address: yuliang.wu@usask.ca.
authors.forename: Yuliang
authors.initials: Y
authors.lastname: Wu
mesh_terms: D004277:DNA, Single-Stranded / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000737:chemistry*; D006801:Humans; D017510:Protein Folding; D055503:Protein Multimerization; D012313:RNA / Q000378:metabolism
chemical_list: D004277:DNA, Single-Stranded; D004268:DNA-Binding Proteins; D012313:RNA
keywords: C-terminus; DNA binding; NABP1; NABP2; OB fold; RNA binding