Abstract
Two new polypeptides, termed ISG70 and ISG64, have been found in Trypanosoma brucei, using enzyme-catalyzed radioiodination techniques. Both are externally disposed integral membrane glycoproteins, containing N-linked carbohydrate chains. No structural homology was detected between ISG70, ISG64, or the variant surface glycoprotein (VSG) when assessed by 1) comparative peptide mapping, 2) immunoprecipitation analysis, and 3) lectin affinity chromatography. ISG70 occurred in 5.1 x 10(4) copies/cell and has been purified 880-fold from detergent extracts of plasma membranes by a procedure that includes gel filtration, lectin affinity chromatography, and preparative SDS-polyacrylamide gel electrophoresis. ISG70 was present only in bloodstream forms and was specifically detected in six different cloned variants from the Molteno Institute trypanosomal antigen type (MITat) serodeme of T. brucei and from the single cloned variant of the International Laboratory for Research on Animal Diseases trypanosomal antigen type (ILTat) serodeme that was examined. Rabbits with chronic infections of T. brucei displayed circulating antibodies against ISG70. Both the immunogenicity of ISG70 and its invariant nature suggest that it may be useful in the development of an effective serodiagnostic test. Furthermore, its stage-specific location combined with its invariant nature implies that its function is strictly related to a physiological role required for the parasite's residence in its mammalian host.
Highlights
The Identification, Purification, and Characterizationof Two Invariant Surface Glycoproteins Located beneath the Surface Coat Barrier of Bloodstream Forms ofTrypanosoma brucei”
Cycles of antigenicvariationinitiated with live cells of a Neither ISG70 nor ISGs, Is Structurally Related to the different variant (MITat1.2) precipitated bothISGs but variant surface glycoprotein (VSG)-Following SDS-PAGE of whole cells (MITat l.l),the failed to recognize the VSG. These results demonstrate the bands of radioiodinated ISGYo, ISGs4,and VSG were cut from structural differences between the ISGs and the VSG from the gel, and each protein was peptide mapped using N-chlo- both homologous and heterologous variants of T. brucei and rosuccinimide under conditions that have been shown previ- indicate the capacity of ISGs to elicit an immune response ously to promote specific cleavage of tryptophanyl peptide independent of the VSG during thecourse of a natural infecbonds [48]
Twonovel and previously undescribed invariant surface glycoproteins of M, 70,000 (ISG70)and 64,000 (ISG,) that were detected during the surface labeling of bloodstream forms of T. brucei with lzSIhave beencharacterized
Summary
Cell Surface Radioiodination Detects Two Previously Unii' i dentifiedAntigens on the External Surface of Bloodstream. Surface-radiolabeled cells (approximately 2 X 10') were subjected either to SDS-PAGE ( A ) followed by staining with Coomassie Blue, drying, and autoradiography. InvarianGt Slyucrofapcreoteins of T. brucei (not shown) separatedISGyo from the bulk of the membrane SDS-PAGE analysisof the ConA-purified material (Fig. 3, proteins which chromatographed asa large skewedpeak close track e) shows that a faint Coomassie Blue-stained band in to theexcluded volumeof the Ultrogel AcA 34 column Each value given is the meanf S.E. of the number of separate determinations shown in parentheses
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
