Homologies Between Different Forms of 2-5A Synthetases
(2′-5′) Oligoadenylate synthetases (2-5A synthetases; EC 126.96.36.199) are present in mammalian cells and tissues and synthesize from ATP a series of oligomers termed 2-5A [general formula: ppp(A2′p)nA; with 1 ≤ n < 18 and usually 1 ≤ n < 6] (Hovanessian 1991). For full enzymic activity of the 2-5A synthetases, binding of double-stranded RNA is required (Sen 1982). Three principal 2-5A synthetase isoenzymes have been described with Mr’s of 40–46, 69, and 100 kDa (Chebath et al. 1987; Hovanessian et al. 1987, 1988). In the following they are classified as 2-5A synthetase I [Mr 40–46 000], II [Mr 69 000] and III [Mr 100 000]. All three isoforms are induced in cells by interferon (Cohen et al. 1988; Rutherford et al. 1988). 2-5A synthetases I and II are present in both the nucleus and the mitochondria as well as in the rough/smooth microsomal fraction, while 2-5A synthetase III is associated with the rough microsomal fraction only (Hovanessian et al. 1987). The enzymic product, 2-5A, functions as an activator of the endoribonuclease L. 2-5A is rapidly degraded either by the relatively unspecific phosphodiesterase (Schmidt et al. 1979; Johnston and Hearl 1987) or the specific 2′,3′-exoribonuclease (Müller et al. 1980; Schröder et al. 1980, 1984).
KeywordsSynthetase Gene Ehrlich Ascites Tumor Cell Oligoadenylate Synthetase Protein Secondary Structure Prediction Helical Wheel
Unable to display preview. Download preview PDF.
- Hovanessian AG, Laurent AG, Chebath J, Galabru J, Robert N, Svab J (1987) Identification of 69-kd and 100-kd forms of 2-5A-synthetase from interferon-treated human cells by specific monoclonal antibodies. EMBO J 5:1273–1280.Google Scholar
- PC/Gene (1991) User and reference manual; release 6.5. IntelliGenetics, Mountain View, CA 2,1991.Google Scholar
- Williams BRG, Silverman RH (eds) (1985) The 2-5A System. Liss, New York.Google Scholar