       Document 0241
 DOCN  M9620241
 TI    Interdomain interactions in the chimeric protein toxin sCD4(178)-PE40: a
       differential scanning calorimetry (DSC) study.
 DT    9602
 AU    Davio SR; Kienle KM; Collins BE; Upjohn Company, Kalamazoo, Michigan
       49007, USA.
 SO    Pharm Res. 1995 May;12(5):642-8. Unique Identifier : AIDSLINE
       MED/96059316
 AB    The thermal denaturation of the chimeric protein toxin known as
       sCD4(178)-PE40 (sCD4-PE40) was studied using differential scanning
       calorimetry (DSC). sCD4-PE40 consists of HIV-binding domains of the
       T-cell membrane protein known as CD4 and the cytotoxic domains of
       Pseudomonas exotoxin A (PE40). sCD4-PE40 undergoes two DSC transitions.
       An endothermic transition associated with unfolding of the CD4 and PE40
       components occurs at approximately 46 degrees C in buffered saline at pH
       6.5. An exothermic transition associated with precipitation of unfolded
       protein occurs at higher temperatures. Both transitions are
       irreversible. DSC studies of solutions of pH 5.0 to 9.5 indicate that
       sCD4-PE40 shows maximal thermal stability at around pH 6.5. Variable pH
       experiments are also presented on solutions of sCD4(183) and PE40
       revealing how these components denature as independent structural
       entities. sCD4(183) denaturation occurs at significantly higher
       temperatures than does the CD4 component of sCD4-PE40. PE40 denaturation
       occurs at the same temperatures as sCD4-PE40. These results suggest that
       the native CD4 and PE40 components are independent and non-interacting
       entities in the chimeric sCD4-PE40 molecule and that unfolding of the
       less-stable PE40 component induces unfolding of the CD4 component. These
       destabilizing interdomain interactions of sCD4-PE40 are in contrast to
       the stabilizing interactions which apparently exist in wild-type
       Pseudomonas exotoxin A between its PE40 domains and the cell binding
       domain of the native toxin (analogous to the CD4 component in
       sCD4-PE40). Reasons are discussed why the type of interdomain
       interactions observed for sCD4-PE40 might be the norm for chimeric
       proteins.
 DE    Antigens, CD4/*CHEMISTRY  Bacterial Toxins/*CHEMISTRY  Calorimetry,
       Differential Scanning  Chemistry, Physical  Chimeric Proteins/*CHEMISTRY
       Chromatography/METHODS  Drug Stability  Exotoxins/*CHEMISTRY  Heating
       Immunotoxins/*CHEMISTRY  Molecular Weight  Protein Denaturation
       Recombinant Proteins/CHEMISTRY  Thermodynamics  JOURNAL ARTICLE

       SOURCE: National Library of Medicine.  NOTICE: This material may be
       protected by Copyright Law (Title 17, U.S.Code).

