Biomedical subjects

Heidi A Ernst

Publications and source records attributed to Heidi A Ernst.

4 recordsLinked to original sources

PubMed2006

Structure of the Sulfolobus solfataricus alpha-glucosidase: implications for domain conservation and substrate recognition in GH31.

The crystal structure of alpha-glucosidase MalA from Sulfolobus solfataricus has been determined at 2.5Angstrom resolution. It provides a structural model for enzymes representing the major specificity in glycoside hydrolase family 31 (GH31), including alpha-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, alpha-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-alpha1,4-Glc), whereas YicI prefers isoprimeverose (Xyl-alpha1,6-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 beta-octyl-glucopyranoside has been determined. It reveals Arg400, Asp87, Trp284, Met321 and Phe327 as invariant residues forming the +1 subsite in the GH31 alpha-glucosidases. Structural comparisons with other GH families suggest that the GH31 enzymes belong to clan GH-D.

Amino Acid Sequence↗

PubMed2005

NAC transcription factors: structurally distinct, functionally diverse.

NAC proteins constitute one of the largest families of plant-specific transcription factors, and the family is present in a wide range of land plants. Here, we summarize the biological and molecular functions of the NAC family, paying particular attention to the intricate regulation of NAC protein level and localization, and to the first indications of NAC participation in transcription factor networks. The recent determination of the DNA and protein binding NAC domain structure offers insight into the molecular functions of the protein family. Research into NAC transcription factors has demonstrated the importance of this protein family in the biology of plants and the need for further studies.

Amino Acid Sequence↗

PubMed2004

Structure of the conserved domain of ANAC, a member of the NAC family of transcription factors.

The structure of the DNA-binding NAC domain of Arabidopsis ANAC (abscisic-acid-responsive NAC) has been determined by X-ray crystallography to 1.9A resolution (Protein Data Bank codes 1UT4 and 1UT7). This is the first structure determined for a member of the NAC family of plant-specific transcriptional regulators. NAC proteins are characterized by their conserved N-terminal NAC domains that can bind both DNA and other proteins. NAC proteins are involved in developmental processes, including formation of the shoot apical meristem, floral organs and lateral shoots, as well as in plant hormonal control and defence. The NAC domain does not possess a classical helix-turn-helix motif; instead it reveals a new transcription factor fold consisting of a twisted beta-sheet surrounded by a few helical elements. The functional dimer formed by the NAC domain was identified in the structure, which will serve as a structural template for understanding NAC protein function at the molecular level.

Amino Acid Sequence↗

PubMed2002

Crystallization and preliminary X-ray analysis of Alicyclobacillus acidocaldarius endoglucanase CelA.

Crystallization of a family 9 beta-1,4-glucanase from the thermoacidophilic bacterium Alicyclobacillus acidocaldarius CelA is reported. Thin plates can be obtained by hanging-drop vapour-diffusion crystallization in high concentrations (60%) of MPD. These crystals are unusual in that they do not bind the dye IZIT in the mother liquor and do not appear to dissolve in water after three weeks or in the storage buffer after 2 d. The crystals diffract weakly and the diffraction pattern is compatible with crystal disorder in one direction. After testing several crystals at the ESRF beamlines ID14-1 and ID14-2, a crystal was found which gave ordered diffraction in all directions. A full data set was collected to 3.0 A resolution, which allowed unambiguous determination of the space group as P2(1)2(1)2 and the unit-cell parameters as a = 85, b = 129.7, c = 48.6 A. Initial promising results from molecular-replacement searches are reported.

Bacillus↗