Correction. In the article "Interactions between molecules (subfactors) released by different T cell sets that yield a complete factor with biological (suppressive) activity" by Wlodzimierz Ptak, R. W. Rosenstein, and Richard K. Gershon, which appeared in number 7, April 1982, ofProc. NatL Acad. Sci. USA (79, 2375-2378 ABSTRACT Multiple molecular forms of immunoreactive corticotropin (ACTH) and ,-endorphin were present in extracts of a unicellular eukaryote (Tetrahymena pynformis). One form of immunoreactive ACTH reacted similarly with two different ACTH antisera (one specific for the 11-24 sequence and the other with determinants within sequences 1-14 and 17-39) and migrated with synthetic hACTH-(1-39) in a gel filtration system. This form also exhibited ACTH bioactivity in a dispersed rat adrenal cell bioassay system, with a mean immunoassay/bioassay ratio of 1.5. Gel filtration revealed multiple size classes of immunoreactive (-endorphin; a major peak of radioreceptor activity was detected which exhibited a Kav similar to that of authentic P-endorphin. A major portion of immunoreactive (3-endorphin-sized material exhibited retention times similar to those of synthetic human and camel 3-endorphin upon reverse-phase high-pressure liquid chromatography. These distinctive properties and specificities would seem to exclude the presence oflimited homologies with sequences present in other proteins. High molecular weight material containing both ACTH and 3-endorphin antigenic determinants was also demonstrated, suggesting, but not proving, the presence of a common precursor molecule.In recent years, classic neuropeptides have been discovered in extraneural vertebrate tissues (1), and both gut and pituitary hormones have been found in the brain (2). We Assay Methods. ACTH radioimmunoassay (4). Two antisera were used. Antiserum 7C, raised in a rabbit, contains antibody molecules directed toward determinants in the NH2-terminal region ofthe ACTH molecule. ACTH-(1-13) and human ACTH-(1-39) (hACTH) react on an equimolar basis; a-melanotropin (melanocyte-stimulating hormone) reacts in a parallel fashion at approximately 58% molar crossreactivity. Rat "pro-opiocortin" (the ACTH-lipotropin precursor molecule) purified from pituitary intermediate lobe by gel filtration and ion exchange chromatography also reacts with the antiserum on an approximately 70% molar basis, whereas a-, P3,-endorphin, -endorphin, and human 3-lipotropin do not crossreact. Four microliters ofthis antiserum is sufficient to completely immunoprecipitate 2.7 pmol ofhACTH-(1-39). The West antiserum (National Abbreviations: F3CCOOH, trifluoroacetic acid; CH3CN, acetyl nitrile; ACTH, corticotropin (adrenocorticotropic hormone); hACTH, human ACTH. ¶ To whom reprint requests should be addressed.
2086The publication costs ofthis article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U. S. C. §1734 solely to indicate this fact.Proc. Natl. Acad. Sci. USA 79 (1982) 2087 Instit...