Heparan Alpha Glucosaminide-N-Acetyltransferase (HGSNAT)
HGNAT; MPS3C; TMEM76; Transmembrane Protein 76
and the mouse ortholog and demonstrated that it is the gene that encodes the lysosomal N-acetyltransferase. HGSNAT did not show structural similarity to any known prokaryotic or eukaryotic N-acetyltransferase or to other lysosomal proteins, on the basis of sequence homology searches. The authors suggested that this enzyme belongs to a new structural class of proteins that transport the activated acetyl residues across the cell membrane.
The deduced 656-amino acid protein with a calculated molecular mass of 73 kD contains an N-terminal signal peptide, 4 putative N-glycosylation sites, and 11 transmembrane domains. Topology modeling predicted the N terminus to be inside the lysosome and the C terminus to be cytosolic.