N-terminal domain of M1P_guanylyl_A_ like proteins are likely to be a isoform of GDP-mannose pyrophosphorylase.
N-terminal domain of the M1P-guanylyltransferase A-isoform like proteins: The proteins of this family are likely to be a isoform of GDP-mannose pyrophosphorylase. Their sequences are highly conserved with mannose-1-phosphate guanyltransferase, but generally about 40-60 bases longer. GDP-mannose pyrophosphorylase (GTP: alpha-d-mannose-1-phosphate guanyltransferase) catalyzes the formation of GDP-d-mannose from GTP and alpha-d-mannose-1-Phosphate. It contains an N-terminal catalytic domain that resembles a dinucleotide-binding Rossmann fold and a C-terminal LbH fold domain. GDP-d-mannose is the activated form of mannose for formation of cell wall lipoarabinomannan and various mannose-containing glycolipids and polysaccharides. The function of GDP-mannose pyrophosphorylase is essential for cell wall integrity, morphogenesis and viability. Repression of GDP-mannose pyrophosphorylase in yeast leads to phenotypes including cell lysis, defective cell wall, and failure of polarized growth and cell separation.