{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,10]],"date-time":"2026-06-10T16:32:48Z","timestamp":1781109168647,"version":"3.54.1"},"reference-count":0,"publisher":"National Academy of Sciences","issue":"17","content-domain":{"domain":["www.pnas.org"],"crossmark-restriction":true},"short-container-title":["Proc. Natl. Acad. Sci. U.S.A."],"published-print":{"date-parts":[[1984,9]]},"abstract":"<jats:p>A eukaryotic initiation factor 2 (eIF-2)-ancillary protein factor Co-eIF-2 promotes displacement of GDP from eIF-2 X GDP and facilitates ternary complex (Met-tRNAf X eIF-2 X GTP) formation in the presence of Mg2+. Heme-regulated protein synthesis inhibitor, HRI, phosphorylates the alpha-subunit of eIF-2 and thus inhibits ternary complex formation as Co-eIF-2 does not displace GDP from eIF-2 alpha (P) X GDP. RF, a high molecular weight cell supernatant factor, reverses protein synthesis inhibition in heme-deficient reticulocyte lysates and also reverses HRI inhibition of ternary complex formation. RF contains Co-eIF-2 activity. In addition, an active RF preparation contains excess alpha-subunit of eIF-2 in the free and unphosphorylated form and this alpha-subunit of eIF-2 is not phosphorylated by HRI and ATP. In this paper we report (i) an active RF preparation contains excess alpha-subunit of eIF-2 and this alpha-subunit can be phosphorylated by HRI and ATP in the presence of GDP; (ii) RF promotes ternary complex formation by eIF-2 X [3H]GDP with accompanying GDP displacement; (iii) in the presence of HRI and ATP, RF promotes ternary complex formation by eIF-2 X [3H]GDP without accompanying GDP displacement; (iv) in the presence of HRI and ATP, the ternary complex formed using RF is active in Met-tRNAf X 40S initiation complex formation; (v) both the ternary complex and the Met-tRNAf X 40S complex formation in the presence of HRI and ATP are completely inhibited by prior incubation of RF with GDP; (vi) upon further fractionation of an active RF fraction, a preparation can be obtained that contains HRI-sensitive Co-eIF-2 activity. However, this preparation does not efficiently reverse protein synthesis inhibition in heme-deficient reticulocyte lysates and does not contain excess alpha-subunit of eIF-2. Based on these observations, we have suggested (a) RF provides the unphosphorylated alpha-subunit to eIF-2 alpha (P) X GDP and restores eIF-2 activity. This RF activity is inhibited as the alpha-subunit in the RF preparation becomes phosphorylated by HRI and ATP in the presence of GDP; (b) RF contains Co-eIF-2 activity, which has dual functions: (i) stimulation of ternary complex formation by eIF-2 and (ii) GDP displacement from eIF-2 X GDP during ternary complex formation. In the presence of HRI and ATP, Co-eIF-2 but does not displace GDP from eIF-2 alpha(P) X GDP.<\/jats:p>","DOI":"10.1073\/pnas.81.17.5379","type":"journal-article","created":{"date-parts":[[2006,5,31]],"date-time":"2006-05-31T05:28:21Z","timestamp":1149053301000},"page":"5379-5383","update-policy":"https:\/\/doi.org\/10.1073\/pnas.cm10313","source":"Crossref","is-referenced-by-count":15,"title":["Protein synthesis in rabbit reticulocytes: a study of the mechanism of action of the protein factor RF that reverses protein synthesis inhibition in heme-deficient reticulocyte lysates."],"prefix":"10.1073","volume":"81","author":[{"given":"M","family":"Grace","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"M","family":"Bagchi","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"F","family":"Ahmad","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"T","family":"Yeager","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"C","family":"Olson","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"I","family":"Chakravarty","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"N","family":"Nasrin","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"A","family":"Banerjee","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"N K","family":"Gupta","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"341","published-online":{"date-parts":[[1984,9]]},"container-title":["Proceedings of the National Academy of Sciences"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/pnas.org\/doi\/pdf\/10.1073\/pnas.81.17.5379","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2022,4,13]],"date-time":"2022-04-13T12:00:21Z","timestamp":1649851221000},"score":1,"resource":{"primary":{"URL":"https:\/\/pnas.org\/doi\/full\/10.1073\/pnas.81.17.5379"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[1984,9]]},"references-count":0,"journal-issue":{"issue":"17","published-print":{"date-parts":[[1984,9]]}},"alternative-id":["10.1073\/pnas.81.17.5379"],"URL":"https:\/\/doi.org\/10.1073\/pnas.81.17.5379","relation":{},"ISSN":["0027-8424","1091-6490"],"issn-type":[{"value":"0027-8424","type":"print"},{"value":"1091-6490","type":"electronic"}],"subject":[],"published":{"date-parts":[[1984,9]]},"assertion":[{"value":"1984-09-01","order":2,"name":"published","label":"Published","group":{"name":"publication_history","label":"Publication History"}}]}}