Functional expression of concatenated ASIC1a fusion proteins.

A: Representative recording of an ASIC1a current in Xenopus oocytes expressing a fusion protein made of three ASIC1a subunit proteins, each with intact C-termini, and linked in a head to tail fashion (3xFP). B: Average (mean ± SD) of ASIC1a currents elicited at pH 6.0 measured in Xenopus oocytes expressing monomeric hASIC1a (wt or G433C mutant) or fusion proteins made of two (2xFP), three (3xFP), or four (4xFP) ASIC1a subunit proteins. All constructs comprise a single, N-terminal, His₈ tag. C: Anti-ASIC1a western blot obtained from oocytes expressing the same ASIC1a constructs as in B; I, II, III, IV have the same meaning as in Fig 3A. D: Relationship between the molecular weights of bands I, II, III, IV estimated from ASIC1a oligomers crosslinked with BMOE (as in Fig 3A) and the size (kDa) of dimeric (gray), trimeric (red) and tetrameric (blue) ASIC1a fusion proteins; the straight dotted line represents the linear regression fit forced to the axes origin; the slope of the regression line is 0.993 ± 0.052.