A-sarcin

This report was the first of its type to show the ability of such a large covalently linked carbohydrate (neomycin) to aid in RNA-DNA hybrid complex-ation. N-Neo-conjugate and a 7-base-long RNA sequence present in a-sarcin loop can form a stable hybrid duplex. The stability of a hybrid duplex with addition of one neomycin equivalent is comparable to the stability of a hybrid duplex where the DNA has a covalent bond to neomycin. The presence of a single mismatch decreases the melting temperature of both neomycin-conjugated... 

Panopoulos P, Dresios J, Synetos D (2004) Biochemical evidence of translational infidelity and decreased peptidyltransferase activity by a sarcin/ricin domain mutation of yeast 25S rRNA. Nucleic Acids Res... 

R/S domain, highly conserved ricin/a-sarcin-interacting domain of 28S rRNA RA-R, retinoic acid receptor RER, rough endoplasmic reticulum Rha, rhamnose, rhamnoside,... 

Sacco G, Drickamer K, Wool IG The primary stracture of the cytotoxin a-sarcin. J Biol Chem 1983 258 5811-5818. 

A satisfactory correlation has been found to exist between sensitivity of archaeal ribosomes to certain antibiotics (streptomycin, erythromycin, a-sarcin) and possession of the specific structural motifs that are involved in antibiotic action. 

There are several instances, however, in which the correlation between antibiotic sensitivity and possession of the prerequisite elements for antibiotic action is less straightforward. This is exemplified by thiostrepton, monosubstituted and disubstituted 2-deoxystreptamines and a-sarcin. 

Presumably, the insensitivity to aminoglycosides, and weak susceptibility to a-sarcin, are accounted for by unique three-dimensional features of the interacting site. 

Fig. 9. The a-sarcin target loop of large ribosomal subunit RNA. The a-sarcin cleaving site is indicated by the arrow (right). The boxed 14-nucleotide stretch is universally conserved, except for the encircled residue which is a cytosine in all bacteria and an adenine in all archaea and eucarya.

RNA interaction and therefore cannot be recommended for probing experiments (e.g. RNase SI and RNase U2 have a pH optimum of 4.5 which prevents or destabilises protein-RNA complex formation). RNase A has a high affinity for a pyrimidine-adenosine stretch (particularly UA), so it can therefore be difficult to obtain single-hit kinetics (except for the UA sequence). Furthermore, RNase A exhibits an endogenous helix unfolding property which makes structure assignment difficult. RNases such as RNase CL3 and a-sarcin are inhibited by Mg2+ which is required for the stability of many complexes and also for proper folding of RNA. 

Various plant toxins, mostly ribosome-inactivating proteins (RIPs), have been identified that bind to any mammalian cell surface expressing galactose units and are subsequently internalized by RME (67). Toxins such as nigrin b (68), a-sarcin (69), ricin and saporin (70), viscumin (71), and modeccin (72) are highly toxic upon oral administration (i.e., are rapidly internalized). The possibility exists, therefore, that modified and, most important, less toxic subunits of these compound can be used to facilitate the uptake of macro-molecular compounds or microparticulates. 

Type I RIPs comprise a single polypeptide chain for example, a-sarcin, an extracellular cytotoxin produced by Aspergillus giganteus, consists of a single chain of 150 amino acid residues. 

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