TY - JOUR
T1 - Structure of the Sulfolobus solfataricus alpha-glucosidase: Implications for domain conservation and substrate recognition in GH31
AU - Ernst, Heidi Asschenfeldt
AU - Lo Leggio, Leila
AU - Willemoes, M.
AU - Leonard, G. A.
AU - Blum, P.
AU - Larsen, Sine
N1 - Keywords: glycoside hydrolase; substrate specificity; a-glucosidase; a-xylosidase; crystal structure
PY - 2006
Y1 - 2006
N2 - The crystal structure of a-glucosidase MalA from Sulfolobus solfataricus has been determined at 2.5 Å resolution. It provides a structural model for enzymes representing the major specificity in glycoside hydrolase family 31 (GH31), including a-glucosidases from higher organisms, involved in glycogen degradation and glycoprotein processing. The structure of MalA shows clear differences from the only other structure known from GH31, a-xylosidase YicI. MalA and YicI share only 23% sequence identity. Although the two enzymes display a similar domain structure and both form hexamers, their structures differ significantly in quaternary organization: MalA is a dimer of trimers, YicI a trimer of dimers. MalA and YicI also differ in their substrate specificities, as shown by kinetic measurements on model chromogenic substrates. In addition, MalA has a clear preference for maltose (Glc-a1,4-Glc), whereas YicI prefers isoprimeverose (Xyl-a1,6-Glc). The structural origin of this difference occurs in the -1 subsite where MalA residues Asp251 and Trp284 could interact with OH6 of the substrate. The structure of MalA in complex with ß-octyl-glucopyranoside has been determined. It reveals Arg400, Asp87, Trp284, Met321 and Phe327 as invariant residues forming the +1 subsite in the GH31 a-glucosidases. Structural comparisons with other GH families suggest that the GH31 enzymes belong to clan GH-D.
AB - The crystal structure of a-glucosidase MalA from Sulfolobus solfataricus has been determined at 2.5 Å resolution. It provides a structural model for enzymes representing the major specificity in glycoside hydrolase family 31 (GH31), including a-glucosidases from higher organisms, involved in glycogen degradation and glycoprotein processing. The structure of MalA shows clear differences from the only other structure known from GH31, a-xylosidase YicI. MalA and YicI share only 23% sequence identity. Although the two enzymes display a similar domain structure and both form hexamers, their structures differ significantly in quaternary organization: MalA is a dimer of trimers, YicI a trimer of dimers. MalA and YicI also differ in their substrate specificities, as shown by kinetic measurements on model chromogenic substrates. In addition, MalA has a clear preference for maltose (Glc-a1,4-Glc), whereas YicI prefers isoprimeverose (Xyl-a1,6-Glc). The structural origin of this difference occurs in the -1 subsite where MalA residues Asp251 and Trp284 could interact with OH6 of the substrate. The structure of MalA in complex with ß-octyl-glucopyranoside has been determined. It reveals Arg400, Asp87, Trp284, Met321 and Phe327 as invariant residues forming the +1 subsite in the GH31 a-glucosidases. Structural comparisons with other GH families suggest that the GH31 enzymes belong to clan GH-D.
U2 - 10.1016/j.jmb.2006.02.056
DO - 10.1016/j.jmb.2006.02.056
M3 - Journal article
SN - 0022-2836
VL - 358
SP - 1106
EP - 1124
JO - Journal of Molecular Biology
JF - Journal of Molecular Biology
IS - 4
ER -