4krd
Crystal Structure of Pho85-Pcl10 Complex
Structural highlights
FunctionPHO85_YEAST Cyclin-dependent protein kinase (CDK) catalytic subunit that regulates multiple cell cycle and metabolic processes in response to nutrient availability. Associates with different cyclins, that control kinase activity, substrate-specificity and subcellular location of the kinase. Favorable growth conditions always result in activated cyclin-CDK complexes. Regulates metabolic processes when associated with PHO80 cyclin family members (PH080, PCL6, PCL7, PCL8 and PCL10), and cell cycle and morphogenesis processes when associated with PCL1,2 cyclin family members (PCL1, PCL2, CLG1, PCL5 and PCL9). When associated with PHO80, negatively regulates the expression of phosphate-starvation-responsive genes under phosphate-rich conditions. The PHO80-PHO85 cyclin-CDK holoenzyme phosphorylates and inactivates the transcription factor PHO4 by promoting its export to the cytoplasm. PHO80-PHO85 phosphorylates and inactivates protein kinase RIM15 by retaining it in the cytoplasm, antagonizing RIM15-induced entry into stationary phase. PHO80-PHO85 also phosphorylates and inactivates the calcineurin-responsive transcription factor CRZ1, linking cyclin-CDK activity to calcium signaling. Together with the cyclins PCL6/PCL7 and PCL8/PCL10, negatively controls glycogen accumulation. When associated with cyclins PCL6 and PCL7, controls glycogen phosphorylase and glycogen synthase activities. PCL6-PHO85 and PCL7-PHO85 phosphorylate and inactivate the phosphatase PP1-2 inhibitor GLC8, causing activation of PP1-2, which then dephosphorylates and activates glycogen phosphorylase. When associated with cyclins PCL8 and PCL10, has glycogen synthase kinase activity. PCL10-PHO85 phosphorylates and negatively regulates glycogen synthase GSY2. Association with PCL1 and PCL2 is required for cell cycle progression at start in the absence of the CDC28-dependent G1 cyclins CLN1 and CLN2. PCL1-PHO85 is involved in phosphorylation of the CDK inhibitor (CKI) SIC1, which is required for its ubiquitination and degradation, releasing repression of b-type cyclins and promoting exit from mitosis. When associated with cyclins PCL1 and PCL2, positively controls degradation of sphingoid long chain base kinase LCB4 via phosphorylation of LCB4, which is required for its ubiquitination and degradation. PCL1-PHO85 also phosphorylates HMS1, NCP1 and NPA3, which may all have a role in mitotic exit. PCL2-PHO85 also phosphorylates RVS167, linking cyclin-CDK activity with organization of the actin cytoskeleton. When associated with PCL5, positively controls degradation of transcription factor GCN4 via phosphorylation of GCN4, which is required for its degradation by the E3 ubiquitin ligase complex SCF(Cdc4). When associated with PCL9, may have a role in bud site selection in G1 phase. PHO85 also phosphorylates the transcription factor SWI5.[1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22] Publication Abstract from PubMedPho85 is a versatile cyclin dependent kinase (CDK) found in budding yeast that regulates a myriad of eukaryotic cellular functions in concert with ten cyclins (called Pcls). Unlike cell cycle CDKs which require phosphorylation of a serine/threonine residue by a CDK-activating kinase (CAK) for full activation, Pho85 require no phosphorylation despite the presence of an equivalent residue. The Pho85-Pcl10 complex is a key regulator of glycogen metabolism by phosphorylating the substrate Gsy2, the predominant, nutritionally regulated form of glycogen synthase. Here we report the crystal structures of Pho85-Pcl10 and its complex with the ATP analog, ATP-gammaS. The structure solidified the mechanism for by-passing CDK phosphorylation to achieve full catalytic activity. An aspartate residue, invariant in all Pcls, acts as a surrogate for the phosphoryl adduct of the phosphorylated, fully activated CDK2, the prototypic cell cycle CDK, complexed with cyclin A. Unlike the canonical recognition motif, SPXK/R, of phosphorylation sites of substrates of several cell cycle CDKs, the motif in the Gys2 substrate of Pho85-Pcl10 is SPXX. CDK5, an important signal transducer in neural development and the closest known functional homolog of Pho85, does not require phosphorylation either, and we found that in its crystal structure complexed with p25 cyclin a water/hydroxide molecule remarkably plays a similar role to the phosphoryl or aspartate group. Comparison between Pho85-Pcl10, phosphorylated CDK2-cyclin A and CDK5-p25 complexes reveals the convergent structural characteristics necessary for full kinase activity and the variations in the substrate recognition mechanism. New Structural Insights into Phosphorylation-free Mechanism for Full CDK-Cyclin Activity and Substrate Recognition.,Zheng F, Quiocho FA J Biol Chem. 2013 Sep 10. PMID:24022486[23] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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