What is it about?
The structure of human brain CutA1 (HsCutA1) has been determined using diffraction data to 2.05 A ̊ resolution. HsCutA1 has been implicated in the anchoring of acetylcholinesterase in neuronal cell membranes, while its bacterial homologue Escherichia coli CutA1 is involved in copper tolerance. Additionally, the structure of HsCutA1 bears similarity to that of the signal transduction protein PII, which is involved in regulation of nitrogen metabolism. Although several crystal structures of CutA1 from various sources with different rotation angles and degrees of interaction between trimer interfaces have been reported, the specific functional role of CutA1 is still unclear. In this study, the X-ray structure of HsCutA1 was determined in space group P212121, with unit-cell parameters a = 68.69, b = 88.84, c = 125.33 A ̊ and six molecules per asymmetric unit. HsCutA1 is a trimeric molecule with intertwined antiparallel -strands; each subunit has a molecular weight of 14.6 kDa and contains 135 amino-acid residues. In order to obtain clues to the possible function of HsCutA1, its crystal structure was compared with those of other CutA1 and PII proteins.
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Why is it important?
The CutA1 homologues in eukaryotes are very well conserved, with the exception of the N-terminal hydro- phobic domain. HsCutA1 is also a homologue of the CutA1 proteins from several bacteria, including Escherichia coli CutA1 (EcCutA1), which is found to be involved in tolerance to Cu2+ and other divalent heavy-metal ions (Fong et al., 1995). Other CutA1 sequences have been obtained by analysis of transcripts and no function is known for the corresponding proteins. The CutA1 structures are quite similar to that of the signal transduction protein PII, indicating a possible function of CutA1 in signal transduction (Arnesano et al., 2003). Structural characterization of CutA1 could guide future investiga- tions aimed at understanding the physiological role of the protein. In this study, we describe the detailed structure of the HsCutA1 protein determined at 2.05 A ̊ resolution and identify potential sites for interaction and clues to protein function by comparison with known CutA1 and PII structures.
Perspectives
It can be concluded from the structural data that the functionally important areas of HsCutA1 appear to be the putative active-site clefts and the flexible -hairpins. Oligomerization of HsCutA1 allows the small (14.6 kDa) protein to form a compact cylinder-shaped structure and offers the three -hairpins and clefts sites for specific interactions with other proteins and effector molecules. These regions contain conserved residues and the flexible -hairpin may change conformation on the binding of effectors and/or docking with a receptor. The negatively charged cleft of HsCutA1 reflects the positive charge of the substrate ligands and is readily accessible to solvent. Elucidation of the structure of HsCutA1 might serve as an important initial step towards providing clues to its function. Future work will include determining the natural ligand(s) of this protein in order to illuminate the specific function(s) of HsCutA1. Also, the role of the hydrophobic N-terminal domain, the structure of which has not been solved owing to its flexibility, is as yet unclear.
Dr Bagautdin Bagautdinov
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This page is a summary of: Structure of putative CutA1 fromHomo sapiensdetermined at 2.05 Å resolution, Acta Crystallographica Section F Structural Biology and Crystallization Communications, April 2008, International Union of Crystallography,
DOI: 10.1107/s1744309108009846.
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