Primary Structure of the Nucleic Acid from the 1,4-α-Glucan Branching Enzyme

Abstract

The primary structure of the nucleic acid from the branching enzyme 1,4-1x-~-glucan : 1,4-a-Dglucan 6-a-( 1,4-a-gIucano)-transferase (2.5-S RNA) isolated from rabbit muscles has been elucidated. The polyribonucleotide consists of 31 nucleotides; the unique features of the polyribonucleotide are the unusually high content of modified nucleotides (32 %) and guanine residues (40 %). Apparently 2.5-S RNA belongs to a class of nucleic acids unknown up to now.It is the first time that the structure of a nucleic acid component from a ribonucleoenzyme has been defined. This work is a prerequisite for gaining insight into the intimate activating effect of the polyribonucleotide on the enzyme action.

On the RNA World: Evidence in Favor of an Early Ribonucleopeptide World

“…Some such examples are described below: (1) the 23S ribosomal RNA that seems to be involved in the catalysis of the peptide bond Samaha et al 1995); (2) a polyribonucleotide tenaciously linked to a protein involved in phosphofructokinase activity (Hofer and Pette 1965); (3) a ribonucleoprotein which catalyzes thiol-disulphide exchange in the sea urchin egg (Sakai 1967); (4) a ribonucleoenzyme, the o-diphenol oxidase from potatoes (Balasingam and Ferdinand 1970); and finally, (5) the 1,4-␣-glucan branching enzyme which has a catalytically active RNA (Korneeva et al 1979;Shvedova et al 1987). The first of these examples could refer to a generalized catalysis in the metabolosome model , thus not necessarily implying a widespread use of RNA enzymes.…”

“…This leads to the prediction that catalytically active RNAs must contain many modified bases, just like tRNAs. One such RNA is described in a ribonucleoprotein, 31 nucleotides long, containing 32% of modified nucleosides and thus resembling a tRNA (Korneeva et al 1979;Shvedova et al 1987). This RNA is catalytically active and intervenes in a glucan transfer reaction.…”

Nucleic acid-binding metabolic enzymes: Living fossils of stereochemical interactions?

“…Probably the first demonstration for an enzyme to bind an RNA molecule was the identification of a 31-nucleotide (n0-1ong RNA bound to the 1,4-~glucan branching enzyme (1,4-o~-gBE) from rabbit muscle (Komeeva et al 1979). Probably the first demonstration for an enzyme to bind an RNA molecule was the identification of a 31-nucleotide (n0-1ong RNA bound to the 1,4-~glucan branching enzyme (1,4-o~-gBE) from rabbit muscle (Komeeva et al 1979).…”

The Chemistry of Self-Splicing RNA and RNA Enzymes

“…Recently, however, it was announced that a polysaccharide branching enzyme, 1,4-a-D-glucan: 1,4-a-D-glucan-6a-(1,4-o-glucano) transferase, isolated from rabbit skeletal muscle, has a catalytic subunit composed of RNA (14). The RNA is only 31 nucleotides in length and contains 10 modified bases ofthe sort found in tRNA (72). The level of activity of the RNA alone is actually higher than that of the holoenzyme (RNA + protein) when assayed at 37C in a 2 mM sodium carbonate buffer, pH 7.2.…”