Conserved inserts in the Hsp60 (GroEL) and Hsp70 (DnaK) proteins are essential for cellular growth.
The Hsp60 and Hsp70 chaperones contain a number of conserved inserts that are restricted to particular phyla of bacteria. A one aa insert in the E. coli GroEL and a 21-23 insert in the DnaK proteins are specific for most Gram-negative bacteria. Two other inserts in DnaK are limited to certain groups of proteobacteria. The requirement of these inserts for cellular growth was examined by carrying out complementation studies with temperature-sensitive (T(s)) mutants of E. coli groEL or dnaK. Our results demonstrate that deletion or most changes in these inserts completely abolished the complementation ability of the mutant proteins. Studies with GroEL and DnaK from some other species that either lacked or contained these inserts also indicated that these inserts are essential for growth of E. coli. The DnaK from some bacteria contains a two aa insert that is not found in E. coli. Introduction of this insert into the E. coli DnaK also led to its inactivation, indicating that these inserts are specific for different groups. We postulate that these conserved inserts that are localized in loop regions on protein surfaces, are involved in some ancillary functions that are essential for the groups of bacteria where they are found.
Singh
Bhag
B
Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, L8N 3Z5, Canada.
Gupta
Radhey S
RS
D000595:Amino Acid Sequence; D001419:Bacteria / Q000145:classification / Q000235:genetics; D018834:Chaperonin 60 / Q000737:chemistry / Q000235:genetics* / Q000502:physiology*; D017124:Conserved Sequence; D004926:Escherichia coli / Q000235:genetics / Q000254:growth & development; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000235:genetics* / Q000502:physiology*; D019143:Evolution, Molecular; D005798:Genes, Bacterial; D005816:Genetic Complementation Test; D018840:HSP70 Heat-Shock Proteins / Q000737:chemistry / Q000235:genetics* / Q000502:physiology*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D009154:Mutation; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity; D013696:Temperature
D018834:Chaperonin 60; D029968:Escherichia coli Proteins; D018840:HSP70 Heat-Shock Proteins; D011994:Recombinant Proteins; C063842:dnaK protein, E coli