Amyotrophic lateral sclerosis (ALS) is an untreatable neurodegenerative disease caused by progressive degeneration of motor neurons in the cerebral cortex, brainstem and spinal cord. Up until now, the disease has been associated with mutations in more than 100 genes, including mutations in the ANXA11 gene. Annexin A11 (ANXA11) a Ca2+ regulated phospholipid-binding protein encoded by 505 amino acids that belongs to a larger annexin protein superfamily. ANXA11 is split into two structurally different parts. The C-terminal core contains four annexin domains, which are composed of five alpha helix motifs, in comparison to the extremely variable and disordered N-terminal tail. Because of its intrinsic properties, the structure of the N-terminal tail is yet to be determined. As part of the research work, we prepared shortened versions of the protein; ANXA11dN1-118 had a shortened N-terminal domain by 118 amino acids starting with Ser119 and ANXA11dN-ter starting with Gly179. The sequences for the recombinant proteins were incorporated in bacterial expression vectors pMCSG7 and pMCSG7-GST using ligation independent cloning. We wanted to know whether the GST-tag will increase the protein solubility and reduce its fragmentation, which occurred in previous experiments. Both forms were expressed in the E. coli strain BL21 [DE3] pLysS and isolated using nickel affinity chromatography. We managed to isolate 19,2 mg of ANXA11dN1-118 and 6,4 mg of ANXA11dN-ter protein, which was sufficient for further crystallization experiments. There were no proteolytic cleavages during protein isolation. As part of the research, we also implemented the D40G mutation in ANXA11 wild type protein using site-specific mutagenesis. The mutated form of ANXA11 with D40G mutation is the main cause of ALS in the European population.
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