beta-Glucosylarginine: a new glucose-protein bond in a self-glucosylating protein from sweet corn

In the search for a protein primer for starch synthesis, an autocatalytic self-glucosylating protein has been isolated from sweet corn. Several tryptic peptides were obtained from the [14C]glucosylated protein and were sequenced, corresponding to over 40% of the estimated total sequence (molecular mass 42 kDa). There is no homology with the amino acid sequence of the autocatalytic glycogen primer, glycogenin, nor in respect of the nature of the union between the autocatalytically added glucose and the protein, which, in the case of the corn protein, now named amylogenin, is a novel glucose-protein bond, a single beta-glucose residue joined to an arginine residue.