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4 Acta Biochimica Polonica

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The effect of vanadate on Pichia pastoris growth, protein kinase A activity and ribosomal protein phosphorylation.

100%

Frajnt M. , Cytryńska M. , Jakubowicz T.

Acta Biochimica Polonica

2002

tom 49

nr 4

959-968

It was found that wild type yeast Pichia pastoris can tolerate vanadate concentration as high as 25 mM in the growth medium. Moreover, four vanadate-resistant P. pastoris strains designated JC100/1, JC100/3, JC100/9 and JC100/15 exhibiting tolerance up to 150 mM vanadate were selected. Growth of P. pastoris was correlated with vanadate to vanadyl reduction and its accumulation in the growth medium. In two selected strains, JC100/9 and JC100/15, protein kinase A activity was much higher in comparison to the wild type strain even without vanadate addition to the growth medium. Moreover, in the presence of vanadate, protein kinase A activity was significantly increased in the wild type and the vanadate-resistant JC100/1 and JC100/3 strains. It was also found that phosphorylation of a 40 kDa protein associated with ribosomes occured in all vanadate-resistant strains from the logarithmic, while in the wild type strain from the stationary growth phase. From the presented results it can be concluded that a protein kinase A signalling pathway(s) might be involved in the mechanism of P. pastoris vanadate resistance. The results also indicate a possible role of the 40 kDa protein in protection of P. pastoris against vanadate toxicity.

Protein kinases CKI and CKII are implicated in modification of ribosomal proteins of the yeast Trichosporon cutaneum

100%

Wojda I. , Cytryńska M. , Frajnt M. , Jakubowicz T.

Acta Biochimica Polonica

2002

tom 49

nr 4

947-957

Phosphorylation of acidic ribosomal proteins P1/P2-P0 is a common phenomenon in eukaryotic organisms. It was found previously that in Trichosporon cutaneum, unlike in other yeast species, in addition to the two acidic ribosomal proteins, two other proteins of 15 kDa and 19 kDa of the small ribosomal subunit were phosphorylated. Here we describe two protein kinases: CKI and CKII, which are engaged in the modification of T. cutaneum ribosomal proteins. The acidic ribosomal proteins and the protein of 19 kDa were modified by CKII associated with ribosomes, while the protein of 15 kDa was modified by CKI. Protein kinase CKI was purified from cell-free extract (CKIC) and from ribosomal fraction (CKIR). The molecular mass of CKIC was established at 33 kDa while that of CKIR at 35-37 kDa. A protein of 40 kDa copurified with CKIR but not CKIC. Heparin significantly increased 40 kDa protein phosphorylation level by CKIR. Microsequencing analysis revealed the presence of CKI recognition motifs in the N-terminal fragment of the 40 kDa protein.

Phosphorylation of yeast ribosomal proteins by CKI and CKII in the presence of heparin

100%

Wojda I. , Cytryńska M. , Frajnt M. , Jakubowicz T.

Acta Biochimica Polonica

1999

tom 46

nr 1

211-215

The effect of cAMP and cGMP on the activity and substrate specificity of protein kinase A from methylotrophic yeast Pichia pastoris.

100%

Frajnt M. , Cytryńska M. , Jakubowicz T.

Acta Biochimica Polonica

2003

tom 50

nr 4

1111-1118

Cyclic AMP dependent protein kinase (PKA) from Pichia pastoris yeast cells was found to be activated by either cAMP or cGMP. Analogs of cAMP such as 8-chloro-cAMP and 8-bromo-cAMP were as potent as cAMP in PKA activation while N6,2'-O-dibutyryl-cAMP did not stimulate the enzyme activity. It was shown that protamine sulfate was almost equally phosphorylated in the presence of 1-2 × 10-6 M cAMP or cGMP while other substrates such as Kemptide, ribosomal protein S6, were phosphorylated to a lower extent in the presence of cGMP. It was demonstrated that pyruvate kinase is a substrate of PKA which co-purified with the P. pastoris enzyme. Moreover, pyruvate kinase was phosphorylated by PKA in the presence of cAMP and cGMP to comparable levels.