Protein O-mannosyltransferase; transfers mannose residues from dolichyl phosphate-D-mannose to protein S/T residues; contains a large TMD containing the catalytic pocket and a lumenal β-trefoil-folded MIR domain; acts as a homodimer utilizing a cooperative dual substrate trans-recognition mechanism, with substrate bound by the catalytic pocket of one protomer and the MIR domain of the other; target for new antifungals