ABSTRACT
Ubiquitous Regulatory Mechanism ........................................................................................... 310 Chemistry of Protein Phosphorylation ...................................................................................... 311
Phosphoacceptor Amino Acids ...................................................................................... 311 Mechanisms of Phosphoprotein Modulation .................................................................. 311 Thermodynamics of Protein Phosphorylation ................................................................ 314
Phosphoproteins Can Be Dephosphorylated In Vivo ........................................... 314 In uence of Thermodynamics on Cascade Architecture .................................... 314
Distribution of Protein Kinase and Phosphatase Families among Hyperthermophiles ............ 315 Histidine Kinases and Response Regulators .................................................................. 315 Protein-Histidine and Protein-Aspartate Phosphatases .................................................. 315 Protein-Serine/Threonine/Tyrosine Kinases .................................................................. 317
“Eukaryote-Like” Protein Kinases ...................................................................... 317 Other Protein-Serine/Threonine/Tyrosine Kinases ............................................. 317
Protein-Serine/Threonine/Tyrosine Phosphatases ......................................................... 317 Characteristics of Protein Kinases and Protein Phosphatases from Hyperthermpophiles ....... 318
Histidine Kinases ............................................................................................................ 318 HpkA from Thermatoga maritima ...................................................................... 318 CheA from Thermatoga maritima ....................................................................... 318 HK853 from Thermatoga maritima .................................................................... 319
Eukaryote-Like Protein Kinases .................................................................................... 319 Rio1 and Rio2 from Archaeoglobus fulgidus ...................................................... 319 SsoPK2 and SsoPK3 from Sulfolobus solfataricus ............................................. 319 Ph0512 from Pyrococcus horikoshii ................................................................... 320
Protein Kinases of Undetermined Sequence .................................................................. 320 Protein Phosphatases ...................................................................................................... 320
Protein-Serine/Threonine Phosphatases .............................................................. 320 Protein-Tyrosine Phosphatases ............................................................................ 321
Phosphoproteins from Hyperthermophiles ................................................................................ 321 Two-Component System Phosphoproteins ..................................................................... 321
CheY from Thermotoga maritima ....................................................................... 321 DrrA, DrrB, and DrrD from Thermatoga maritima ........................................... 322 NtrC1 from Aquifex aeolicus ............................................................................... 322
Phosphoserine-and Phosphothreonine-Containing Proteins ......................................... 322 Initiation Factor 2α from Pyrococcus horikoshii ................................................ 322 Cdc6 from Sulfolobus acidocaldarius ................................................................. 323
Phosphohexomutase from Sulfolobus solfataricus .............................................. 323 SsoPK3 from Sulfolobus solfataricus .................................................................. 323
Phosphotyrosine-Containing Proteins ............................................................................ 324 Phosphoproteins of Undetermined Phosphoamino Acid Content .................................. 324
Glycogen Synthase from Sulfolobus acidocaldarius .......................................... 324 d-Gluconate Dehydratase from Sulfolobus solfataricus ..................................... 324 Chaperonin-Associated Aminopeptidase from Sulfolobus solfataricus ............. 325
Physiological Role of Protein Phosphorylation in Hyperthermophiles ..................................... 325 In uence of Temperature ................................................................................................ 325 Protein-Serine/Threonine/Tyrosine Phosphorylation .................................................... 326 Two-Component System ................................................................................................. 326
Conclusion .................................................................................................................................. 327 Acknowledgments ...................................................................................................................... 327 References .................................................................................................................................. 327
The phosphorylation and dephosphorylation of proteins represents one of nature’s most proli c mechanisms for regulating cellular functions. Does protein-phosphorylation play a prominent role in the lives of hyperthermophilic organisms? What proteins are targeted for modi cation by phosphorylation in these extremophiles? The chapter below will try to summarize our current state of knowledge regarding the phosphoproteins, protein kinases, and protein phosphatases found in hyperthermophiles. This information will then be used to consider how extreme temperatures may have shaped the development of their protein phosphorylation cascades.
