KChannelDB: Extraction of mutation data from the literature

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 V59G 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 V59G in IRK11_HUMAN

Relevant sentences:

V59G

• To determine the molecular basis of these different phenotypes , we expressed wild-type or mutant (R201C , Q52R , or V59G) Kir6.2 / sulfonylurea receptor 1 channels in Xenopus oocytes

• All mutations increased resting whole-cell K ATP currents by reducing channel inhibition by ATP , but , in the simulated heterozygous state , mutations causing PNDM alone (R201C) produced smaller K ATP currents and less change in ATP sensitivity than mutations associated with severe disease (Q52R and V59G)

• Our results also show that mutations in the slide helix of Kir6.2 (V59G) influence the channel kinetics , providing evidence that this domain is involved in Kir channel gating , and suggest that the efficacy of sulfonylurea therapy in PNDM may vary with genotype

• (B) Homology model of Kir6.2 (7 ) , indicating the location of residues R201 , Q52R , and V59G associated with neonatal diabetes

• In contrast , the mutations Q52R , V59M , and V59G , which are associated with severe disease , lie some distance from the ATP-binding site , within the N-terminal region of the protein ; moreover , V59 lies within the 'slide helix , ' a domain postulated to be involved in the opening and closing (gating) of Kir channels (7 )

• In this paper , we compare the functional effects of mutations associated with severe disease (Q52R and V59G) with those that cause mild disease (R201C and R201H)

• In contrast , significant resting whole-cell K + currents are present in oocytes expressing homomeric Q52R , V59G , or R201C (homQ52R , homV59G , and homR201C , respectively) (Fig. 2 and Table 1 )

• Whole-cell homV59G and homQ52R currents were not increased further by azide application , as if these channels are fully activated at rest and insensitive to metabolically induced changes in nucleotides

• However , homR201C channels were enhanced by azide , suggesting that they are more ATP-sensitive than homV59G and homQ52R channels

• For heterozygous channels (hetV59G , hetQ52R , and hetR201C) , hetV59G and hetQ52R resting whole-cell currents were of similar amplitude , constituting ~65% of their homomeric values , but were far larger than wild-type currents (Fig. 2B )

• Resting hetR201C currents were smaller than hetQ52R and hetV59G currents but still significantly larger than wild-type (Fig. 2 and Table 1 )

• All homomeric mutant channels were substantially less sensitive to intracellular ATP than wild type , the order of potency being WT > Q52R > R201C > V59G (Table 1 )

• In particular , hetQ52R and hetV59G channels were half-maximally blocked by ATP concentrations of 20-30 µM , whereas the ATP sensitivity of hetR201C channels was higher (11 µM) (Table 1 )

• (Upper Right) Mean relationship between [ATP] and KATP conductance expressed relative to the conductance in the absence of nucleotide for Kir6.2 / SUR1 (open blue circles , n = 6) and heterozygous (red filled circles , n = 6) and homomeric (black filled squares , n = 6) Kir6.2-V59G / SUR1 channels

• For heterozygous V59G , IC50 = 26 µM and h = 1.18

• For homomeric V59G , IC50 = 8.1 mM and h = 0.75

• (Lower Right) Mean relationship between [ATP] and KATP conductance expressed relative to the conductance in the absence of nucleotide for wild type (open blue circles) and hetR201C (filled red circles) , hetQ52R (filled black squares) , and hetV59G (filled green hexagons) channels

• This may explain why mutations that produce a small decrease in the ATP sensitivity of heterozygous channels (R201C and R201H) result in neonatal diabetes alone , whereas those causing a greater reduction (Q52R and V59G) are associated with severe disease

• Thus , the P O(0) of homomeric channels containing the R201C mutation was not significantly different from wild-type , whereas that of homQ52R and homV59G channels was substantially greater (Table 1 )

• Thus , mutations at residue 201 , which lies within the putative ATP-binding site (8 ) , probably act by reducing ATP binding per se , whereas the Q52R and V59G mutations appear to decrease ATP sensitivity indirectly , by favoring the open conformation of the channel

• Because V59G channels have a much lower ATP sensitivity than Q52R channels , despite a similar P O(0) , the V59G mutation is also likely to affect ATP binding and / or the mechanism by which ATP binding is transduced into channel closure

• To determine whether the V59G mutation affects PO(0) directly or indirectly by means of an increase in PIP2 binding , we used neomycin , a polycation that binds to PIP2 , closes KATP channels and has been used to evaluate PIP2 affinity (33 )

• In 3 / 3 patches , 100 µM neomycin did not alter Kir6.2-V59G / SUR1 currents over 5-10 min (data not shown)

• This finding is consistent with the idea that the V59G mutation affects PO(0) directly , rendering gating insensitive to PIP2 modulation

• As Table 1 shows , < ; P O(0)> was significantly higher for hetQ52R and hetV59G channels than wild type

• In the case of the V59G channels , simulations suggest that the mutation must affect both gating and ATP-binding / transduction and indicate that the latter effect is largely suppressed in heterozygous channels containing wild-type subunits (as is the case for hetR201C)

• These findings explain why hetQ52R and hetV59G channels have similar ATP sensitivities despite the very different ATP sensitivities of the homomeric channels

• We observed that 500 µM tolbutamide blocked azide-activated whole-cell currents by 89 ± 1% (n = 12) , 65 ± 5% (n = 9) , and 41 ± 2% (n = 9) for hetR201C , hetQ52R , and hetV59G channels , respectively

F.Horn (kchanneldbcmbi.ru.nl), 17-Aug-2005