Skip to main content

Table 3 Comparison of selective pressure by transmembrane domain.

From: The odorant receptor repertoire of teleost fish

  TM1 TM2 TM3 TM4 TM5 TM6 TM7 non-TM CDS
Length (amino acids) 26 21 19 24 25 19 24 110 268
Mean pairwise dN/dS a 0.330 0.276 0.457 0.574 0.437 0.513 0.282 0.304 0.325
TM vs loops p-value (2 -tailed t test) b 9.9E-04 0.81 2.1E-12 7.6E-21 1.2E-18 2.5E-10 1.00   
TM vs CDS p-value (2 -tailed t test) b 0.45 0.025 2.1E-08 5.9E-16 7.9E-12 6.0E-07 0.0024   
Number of positively selected sites (p < 0.1) c 0 0 1 1 0 0 0 2 4
Number of negatively selected sites (p < 0.1) c 21 16 12 15 15 14 19 80 192
  1. a The mean ratios of non-synonymous substitutions per non-synonymous site (dN) to synonymous substitutions per synonymous site (dS) were calculated for each transmembrane region, the aggregate of the non-transmembrane regions, as well as the entire OR coding sequence. dN/dS ratios were calculated only for pairwise comparisons in which mutational saturation had not been reached. A constant set of 262 informative pairs was used for all calculations.
  2. b Probabilities that the average dN/dS ratio for the particular TM domain is no different than the average for the entire CDS or the non-TM domains, using a two-tailed t test.
  3. c Number of sites with probabilities greater than 0.9 (p < 0.1) of being positively or negatively selected for each domain. Ancestral sequences were reconstructed, and at every non-constant site, dN and dS were calculated. If dN < (or >) dS, a p-value derived from a two-tailed binomial distribution was used to assess significance.