High impact information on CNB1

• Membranes were isolated from the pmr1 pmc1 cnb1 mutant transformed with ECA1 to determine if the ECA1 polypeptide (ECA1p) could be phosphorylated as intermediates of the reaction cycle of Ca2+-pumping ATPases [1].
• Therefore, a double mutant in calcineurin (CNB1) and FKS1 is inviable due to a deficiency in FKS2 expression [2].
• First, deletion of the gene encoding the calcineurin regulatory B subunit, CNB1, from a wild-type strain decreases the LD50 of alpha-factor but has no further effect on a cmd1-6 strain [3].
• Yeast cells lacking functional calcineurin (cna1 cna2 or cnb1 mutants) display growth defects under specific environmental conditions, for example, in the presence of high concentrations of Na+, Li+, Mn2+, or OH- but are indistinguishable from wild-type cells under standard culture conditions [4].
• A PTC4 cDNA that encodes a protein phosphatase belonging to the PP2C family was obtained as a high dosage suppressor of the lethality of Delta cnb1 Delta mpk1 strain [5].

Biological context of CNB1

• A calcineurin-deletion mutation (delta cnb1), which by itself has no detectable effect on growth and morphology, enhanced some phenotypes (slow growth and morphological abnormality) of crv2 and crv3 mutants [6].
• Calcineurin regulatory subunit is essential for virulence and mediates interactions with FKBP12-FK506 in Cryptococcus neoformans [7].
• Although deletion of the genes encoding the yeast catalytic subunits of calcineurin (CNA1 and CNA2) maintain the interaction, absence of the regulatory subunit Cnb1 prevents binding [8].
• DNA sequence analysis of the YCN2 region of chromosome XI in Saccharomyces cerevisiae [9].
• Two genes involved in protein phosphatase activity were identified: YCN2 and an open reading frame encoding a protein that shares 46% amino acid identity with the sds22+ protein from Schizosaccharomyces pombe [9].

Anatomical context of CNB1

• In addition, the K+ transport system of cnb1 delta cells was not converted to the high affinity state that facilitates better discrimination of K+ over Na+ [10].

Associations of CNB1 with chemical compounds

• Yeast mutants defective in a Golgi Ca2+ pump (pmr1) or both Golgi and vacuolar Ca2+ pumps (pmr1 pmc1 cnb1) were sensitive to growth on medium containing 10 mM EGTA or 3 mM Mn2+ [1].
• Membranes were isolated from the pmr1 pmc1 cnb1 mutant transformed with TcSCA, and it was found that the TcSCA polypeptide formed a Ca(2+)-dependent and hydroxylamine-sensitive (32)P-labeled phosphoprotein of 110 kDa in the presence of [gamma-(32)P]ATP [11].
• The Saccharomyces cerevisiae crv mutants (crv1, 2, 3 and 4) exhibit phenotypes, such as calcium resistance and vanadate sensitivity, which are apparently similar to those of calcineurin-deficient mutants [12].

Physical interactions of CNB1

• These mutations do not significantly affect the ability of Cna1p to interact with Cnb1p, calmodulin, or Fkb1p (FK506-binding protein) [13].

Regulatory relationships of CNB1

• The defect in recovery of the delta cnb1 mutant was suppressed by overexpression of MPK1 [6].

Other interactions of CNB1

• These phenotypes of crv2 and crv3 mutants were partially suppressed by Ca2+ or by overproduction of the calcineurin subunits (Cmp2 and Cnb1) [6].
• Thus the cnb1 delta strain resembled a trk1 mutant [10].

Analytical, diagnostic and therapeutic context of CNB1

• Southern blot analysis indicates that the gene for YCNB is a single-copy gene [14].
• Further sequence analysis suggests the presence of three additional genes near YCN2: a mitochondrial acyl-carrier protein, a gene encoding a putative hydrophobic protein, and a new gene coding for a tRNA(Leu) (UAA) isoacceptor located near a delta sequence [9].

References