Genomic organization and chromosomal mapping of the murine alpha 1,2-mannosidase IB involved in N-glycan maturation.

alpha 1,2-Mannosidases are a family of enzymes with similar amino acid sequences that are required for the formation of complex and hybrid N-linked oligosaccharides in mammalian cells. We are reporting the first genomic structure of a member of this enzyme family, the murine alpha 1,2-mannosidase IB gene. Two BALB/c cosmid genomic clones (Cos.31.1 and Cos.25.1) and three overlapping 129/su P1 genomic clones were isolated. Analysis of Cos.31.1 and the P1 clones showed that the alpha 1,2-mannosidase IB gene spans > or = 80 kb of the genome and consists of 13 exons representing the complete open reading frame of the enzyme. Fluorescence in situ hybridization with alpha 1,2-mannosidase IB genomic DNA (Cos.31.1) localized the gene to mouse chromosome 3F2. Sequence analysis of the Cos.25.1 cosmid clone provided evidence for the existence of another related gene or pseudogene. Fluorescence in situ hybridization with Cos.25.1 localized this sequence to mouse chromosome 4A13.