A protein complex capable of protein N-acetylglucosaminyltransferase activity, the addition of nucleotide-activated sugars onto the polypeptide according to reaction: UDP-N-acetyl-D-glucosamine + protein = UDP + 4-N-(N-acetyl-D-glucosaminyl)-protein. The complex has different compositions in different species: In mammals it is often a homotrimer, in bacteria a heterotetramer of 2 different subunits. [ http://www.ncbi.nlm.nih.gov/pubmed/15247246 ]