title: Prediction of solubility on recombinant expression of Plasmodium falciparum erythrocyte membrane protein 1 domains in Escherichia coli.
abstract: BACKGROUND
  Cellular interactions elicited by Plasmodium falciparum erythrocyte membrane protein antigen 1 (PfEMP1) are brought about by multiple DBL (Duffy binding like), CIDR (cysteine-rich interdomain region) and C2 domain types. Elucidation of the functional and structural characteristics of these domains is contingent on the abundant availability of recombinant protein in a soluble form. A priori prediction of PfEMP1 domains of the 3D7 genome strain, most likely to be expressed in the soluble form in Escherichia coli was computed and proven experimentally.
  
  
  METHODS
  A computational analysis correlating sequence-dependent features to likelihood for expression in soluble form was computed and predictions were validated by the colony filtration blot method for rapid identification of soluble protein expression in E. coli.
  
  
  RESULTS
  Solubility predictions for all constituent PfEMP1 domains in the decreasing order of their probability to be expressed in a soluble form (% mean solubility) are as follows: ATS (56.7%) > CIDR1alpha (46.8%) > CIDR2beta (42.9%) > DBL2-4gamma (31.7%) > DBL2beta + C2 (30.6%) > DBL1alpha (24.9%) > DBL2-7epsilon (23.1%) > DBL2-5delta (14.8%). The length of the domains does not correlate to their probability for successful expression in the soluble form. Immunoblot analysis probing for soluble protein confirmed the differential in solubility predictions.
  
  
  CONCLUSIONS
  The acidic terminal segment (ATS) and CIDR alpha/beta domain types are suitable for recombinant expression in E. coli while all DBL subtypes (alpha, beta, gamma, delta, epsilon) are a poor choice for obtaining soluble protein on recombinant expression in E. coli. This study has relevance for researchers pursuing functional and structural studies on PfEMP1 domains.
authors.affiliation: Department of Microbiology, Tumor and Cell Biology (MTC), Karolinska Institutet, P, O, Box 280, Stockholm, S-17177, Sweden. sanjay.ahuja@mtc.ki.se
authors.forename: Sanjay
authors.initials: S
authors.lastname: Ahuja
authors.forename: Satpal
authors.initials: S
authors.lastname: Ahuja
authors.forename: Qijun
authors.initials: Q
authors.lastname: Chen
authors.forename: Mats
authors.initials: M
authors.lastname: Wahlgren
mesh_terms: D000818:Animals; D019295:Computational Biology; D030561:Databases, Nucleic Acid; D030562:Databases, Protein; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D015233:Models, Statistical; D010963:Plasmodium falciparum / Q000235:genetics / Q000378:metabolism*; D011237:Predictive Value of Tests; D015800:Protozoan Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012995:Solubility
chemical_list: D015800:Protozoan Proteins; D011994:Recombinant Proteins; C085731:erythrocyte membrane protein 1, Plasmodium falciparum