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Structural and lipid-binding characterization of human annexin A13a reveals strong differences with its long A13b isoform

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Fernández Lizarbe, Sara and Lecona, Emilio and Santiago Gómez, Angélica and Olmo, Nieves and Lizarbe, María Antonia and Turnay, Javier (2016) Structural and lipid-binding characterization of human annexin A13a reveals strong differences with its long A13b isoform. Biological Chemistry, 398 (3). pp. 359-371. ISSN 1431-6730, ESSN: 1437-4315

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Official URL: https://www.degruyter.com/view/j/bchm.2017.398.issue-3/hsz-2016-0242/hsz-2016-0242.xml?format=INT



Abstract

Annexin A13 is the founder member of the vertebrate family of annexins, which are comprised of a tetrad of unique conserved domains responsible for calcium-dependent binding to membranes. Its expression is restricted to epithelial intestinal and kidney cells. Alternative splicing in the N-terminal region generates two isoforms, A13a and A13b, differing in a deletion of 41 residues in the former. We have confirmed the expression of both isoforms in human colon adenocarcinoma cells at the mRNA and protein levels. We have cloned, expressed, and purified human annexin A13a for the first time to analyze its structural characteristics. Its secondary structure and thermal stability differs greatly from the A13b isoform. The only tryptophan residue (Trp186) is buried in the protein core in the absence of calcium but is exposed to the solvent after calcium binding even though circular dichroism spectra are quite similar. Non-myristoylated annexin A13a binds in a calcium-dependent manner to acidic phospholipids but not to neutral or raft-like liposomes. Calcium requirements for binding to phosphatidylserine are around 6-fold lower than those required by the A13b isoform. This fact could account for the different subcellular localization of both annexins as binding to basolateral membranes seems to be calcium-dependent and myristoylation-independent.


Item Type:Article
Uncontrolled Keywords:Annexin; Calcium binding; Circular dichroism spectroscopy; Fluorescence emission spectroscopy; Phospholipid binding; Thermal stability
Subjects:Medical sciences > Biology > Biochemistry
ID Code:44648
Deposited On:15 Sep 2017 08:57
Last Modified:26 Sep 2017 23:01

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