High impact information on PTK2

• Ptk2 has the strongest effect on Pma1, and ptk2 mutants exhibit a pleiotropic phenotype of tolerance to toxic cations, including sodium, lithium, manganese, tetramethylammonium, hygromycin B, and norspermidine [1].
• Accordingly, ptk2 mutants exhibited reduced uptake of lithium and methylammonium [1].
• A plausible interpretation is that ptk2 mutants have a decreased membrane potential and that diverse cation transporters are voltage dependent [1].
• These results indicate that the putative STK2 Ser/Thr kinase gene is an essential determinant of high-affinity polyamine transport in yeast whereas its close homolog STK1 mostly affects a lower-affinity, low-capacity polyamine transport activity [2].
• A 304-amino-acid stretch comprising 11 of the 12 catalytic subdomains of Stk2p is approximately 83% homologous to the putative Pot1p/Kkt8p (Stk1p) protein kinase, a recently described activator of low-affinity spermine uptake in yeast [2].

Biological context of PTK2

• The nucleotide sequence of the PTK2 gene indicated that it is identical with the YJR059W open reading frame of chromosome X encoding a putative serine/threonine protein kinase [3].
• In magnesium-limited medium, the cell growth of a spermine-sensitive polyamine uptake mutant transformed with PTK2 recovered its sensitivity to spermine [3].
• Deletions of SKY1 or PTK2 in the Saccharomyces cerevisiae trk1Deltatrk2Delta mutant cells exert dual effect on ion homeostasis [4].
• The deduced amino acid sequence of the PTK2 gene product was 38% identical and 55% similar with that of the PTK1 (POT1) gene product, a putative serine/threonine protein kinase, which was found to enhance spermine uptake of the same mutant [3].
• A 747-bp DNA fragment adjacent to the lacZ fusion gene rescued from one MGBG-resistant clone mapped to chromosome X within the coding region of a putative Ser/Thr protein kinase gene of previously unknown function (YJR059w, or STK2) [2].

Anatomical context of PTK2

• Among these latter mutants, three were deleted for genes involved in plasma membrane transport, including the L-carnitine transporter Agp2, as well as the kinases Ptk2 and Sky1, which are involved in regulating polyamine transport [5].

Associations of PTK2 with chemical compounds

• We have isolated a new gene (PTK2) which restores spermine uptake of a polyamine uptake-deficient mutant of Saccharomyces cerevisiae (Kakinuma, Y., Maruyama, T., Nozaki, T., Wada, Y., Oshumi, Y., and Igarashi, K., 1995, Biochem, Biophys. Res. Commun. 216, 985-992) [3].
• Transformation of stk2::lacZ cells with the STK2 gene cloned into a single-copy expression vector restored spermidine transport to wild-type levels [2].
• In this study we find that Ptk2 localized to the plasma membrane in a Triton X-100 insoluble fraction [6].
• Furthermore, we show that the Ptk2 carboxyl terminus is essential for glucose-dependent Pma1 activation and for the phosphorylation of Ser899 [6].

Enzymatic interactions of PTK2

• In vitro phosphorylation assays using a recombinant GST-fusion protein comprising 30 C-terminal amino acids of Pma1 suggest that Ser899 is phosphorylated by Ptk2 [6].

Other interactions of PTK2

• Two yeast kinases, SKY1 and PTK2, have been demonstrated to regulate polyamine tolerance [7].
• Exogenous polyamine deprivation also derepressed residual spermidine transport in stk2::lacZ mutants, but simultaneous disruption of STK1 and STK2 virtually abolished high-affinity spermidine transport under both repressed and derepressed conditions [2].

References