2Institute of Molecular Genetics, Russian Academy of Sciences, 123182 Moscow, Russia
3Shemyakin–Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, 117997 Moscow, Russia
4University of Turku, Turku, 20500, Finland
* To whom correspondence should be addressed.
Received May 4, 2017; Revision received June 2, 2017
In this work, 125I-labeled cholera toxin B-subunit (CT-B) (specific activity 98 Ci/mmol) was prepared, and its high-affinity binding to human blood T-lymphocytes (Kd = 3.3 nM) was determined. The binding of the 125I-labeled CT-B was inhibited by unlabeled interferon-α2 (IFN-α2), thymosin-α1 (TM-α1), and by the synthetic peptide LKEKK, which corresponds to sequences 16-20 of human TM-α1 and 131-135 of IFN-α2 (Ki 0.8, 1.2, and 1.6 nM, respectively), but was not inhibited by the unlabeled synthetic peptide KKEKL with inverted sequence (Ki > 1 µM). In the concentration range of 10-1000 nM, both CT-B and peptide LKEKK dose-dependently increased the activity of soluble guanylate cyclase (sGC) but did not affect the activity of membrane-bound guanylate cyclase. The KKEKL peptide tested in parallel did not affect sGC activity. Thus, the CT-B and peptide LKEKK binding to a common receptor on the surface of T-lymphocytes leads to an increase in sGC activity.
KEY WORDS: peptides, receptors, thymosin-α1, interferon-α, T-lymphocytes