p.E84Q/E285A/E292A/D349N/E358Q Glu84Gln/Glu285Ala/Glu292Ala/Asp349Asn/Glu358Gln (p.E115Q/E316A/E323A/D380N/E389Q Glu115Gln/Glu316Ala/Glu323Ala/Asp380Asn/Glu389Gln in primary sequence with 31 amino-acids signal peptide) Electrostatic attraction hypothesis no significant effect