The Structure of Bovine Lysosomal Alpha-Mannosidase Suggests a Novel Mechanism for Low-Ph ActivationHeikinheimo, P., Helland, R., Leiros, H.S., Leiros, I., Karlsen, S., Evjen, G., Ravelli, R., Schoehn, G., Ruigrok, R., Tollersrud, O.-K., Mcsweeney, S., Hough, E.
(2003) J Mol Biol 327: 631
- PubMed: 12634058
- DOI: https://doi.org/10.1016/s0022-2836(03)00172-4
- Primary Citation of Related Structures:
- PubMed Abstract:
Lysosomal alpha-mannosidase (LAM: EC 220.127.116.11) belongs to the sequence-based glycoside hydrolase family 38 (GH38). Two other mammalian GH38 members, Golgi alpha-mannosidase II (GIIAM) and cytosolic alpha-mannosidase, are expressed in all tissues. In humans, cattle, cat and guinea pig, lack of lysosomal alpha-mannosidase activity causes the autosomal recessive disease alpha-mannosidosis. Here, we describe the three-dimensional structure of bovine lysosomal alpha-mannosidase (bLAM) at 2.7A resolution and confirm the solution state dimer by electron microscopy. We present the first structure of a mammalian GH38 enzyme that offers indications for the signal areas for mannose phosphorylation, suggests a previously undetected mechanism of low-pH activation and provides a template for further biochemical studies of the family 38 glycoside hydrolases as well as lysosomal transport. Furthermore, it provides a basis for understanding the human form of alpha-mannosidosis at the atomic level. The atomic coordinates and structure factors have been deposited in the Protein Data Bank (accession codes 1o7d and r1o7dsf).
Institutt for Kjemi, Universitetet i Tromsø, N-9037, Tromsø, Norway.