Phosphorylation of membrane proteins in response to temperature in an Antarctic Pseudomonas syringae

Temperature-dependent phosphorylation and dephosphorylation of membrane proteins was studied in vitro in a number of psychrotrophic Antarctic bacteria which grow between 0 and 30 degrees C. One of them, a Pseudomonas syringae isolate, was studied in detail and was found to have three membrane proteins of molecular mass 30, 65 and 85 kDa which were phosphorylated differently in response to low and high temperatures. The 65 kDa protein was phosphorylated only at lower temperatures (between 0 and 15 degrees C). The 30 kDa protein was phosphorylated more at higher temperatures and was possibly a histidine kinase. This protein was present in all the psychrotrophic Pseudomonas species studied and in Sphingobacterium antarcticus. A possible role for these proteins in sensing environmental temperature is proposed.