KChannelDB: Extraction of mutation data from the literature 2005, KChannelDB.
This data was extracted from Medline abstracts and full texts (when available) in an automated manner.
The table below describes the selected point mutation and provides links to other documents. The sentence(s) where the point mutation H118E was found are listed after the table.
The mutated residues are also indicated in the family sequence alignments and hyperlinked to the corresponding mutation pages.
Point mutation H118E in KAT1_ARATH
- Normalized representative currents recorded from the wild type KAT1 (this channel will be referred to as H118H) , H118K , H118R , H118D , and H118E channels at pH i = 7.2 in response to voltage pulses to -180 mV are shown in Fig. 5 A
- The negatively charged amino acid mutants , H118D and H118E , were noticeably slower in their activation kinetics than the H118H channel but again very similar to each other
- (B) Henderson-Hasselbalch plot of the normalized t 0.5-pH i relations for the H118E and H118K mutants
- For H118K and H118E , the t 0.5max and t 0.5min values of wild type KAT1 were used because it was difficult to determine the extreme values for these mutant channels
- Within the pH i range of 5.2 to 8.2 , where H118H is very pH i sensitive (see Fig. 2 ) , neither H118E nor H118K showed any marked pH i dependence
- Activation time course of H118E remained slow and mostly independent of pH i and that of H118K remained fast and also independent of pH i in this pH range (Fig. 5 B)
- At the extreme pH i values , however , both H118E and H118K exhibited some pH i dependence
- For example , H118E T A was noticeably and consistently faster at pH i = 4.2 than that at pH i = 5.2 , and H118K T A was slower at pH i = 10.2 than at 8.2 (Fig. 5 B)
- Because t 0.5min for H118E and t 0.5max for H118K could not be obtained , the pH i dependence data were not confidently fitted with the Henderson-Hasselbalch formulation
- However , using pK values of 4.3 and 10.8 , which are often described for the side chains of E and K (Edsall and Wyman , 1958(image) ) , the small pH i dependence of H118E and H118K could be approximated (Fig. 5 B)
- It is also possible that structural determinants other than the amino acid at position 118 are involved in regulating the small pH i sensitivities of the H118E and H118K mutant channels
- The results that T A of H118E is slower and less pH i-dependent than that of H118H predict that T A of KST1 with E at the H118-equivalent position should be slower than that of H118H and similar to that of H118E
- Normalized representative currents through H118H , H118E , and KST1 measured at pH i = 7.2 are compared in Fig. 6 A
- Consistent with the prediction , T A of KST1 was slower than that of H118H and indistinguishable from that of H118E (Fig. 6 A ; also see Fig. 5 of Hedrich and Dietrich , 1996(image) )
- Furthermore , the activation time course of KST1 was much less dependent on pH i than that of H118H but very similar to that of H118E
- At extreme lower pH i , as found with H118E , KST1 T A accelerated (Fig. 6 B)
- (image) View larger version (17K): [in this window] [in a new window] FIGURE 6 Activation time course of H118H , H118E , and KST1
- (A) Scaled representative currents for H118H , H118E , and KST1 elicited at -180 mV , pH i = 7.2
- Single-channel current amplitudes are not affected by the H118 mutations Although the first latencies are affected by the charged H118 mutations , the single-channel amplitudes of the H118 mutants (H118D , H118E , H118K , and H118R) were very similar to that of the wild type KAT1 channel
- The macroscopic currents of H118H and H118E were recorded in the solutions of different ionic strength
- However , T A of both H118H and H118E at pH i = 6.2 where H118 is expected to be protonated , was not markedly affected by the changes in the internal solution ionic strength (data not shown)
- KST1 has a glutamate at the H118-equivalent position , and its T A is similar to that of KAT1 H118E or H118D
- 5 and 14 ) and H118E channels (Fig. 5 )
F.Horn (kchanneldbcmbi.ru.nl), 17-Aug-2005