A cluster of diagnostic Hsp68 amino acid sites that are identified in Drosophila from the melanogaster species group are concentrated around beta-sheet residues involved with substrate binding.
The coding region of the hsp68 gene has been amplified, cloned, and sequenced from 10 Drosophila species, 5 from the melanogaster subgroup and 5 from the montium subgroup. When the predicted amino acid sequences are compared with available Hsp70 sequences, patterns of conservation suggest that the C-terminal region should be subdivided according to predominant secondary structure. Conservation levels between Hsp68 and Hsp70 proteins were high in the N-terminal ATPase and adjacent beta-sheet domains, medium in the alpha-helix domain, and low in the C-terminal mobile domain (78%, 72%, 41%, and 21% identity, respectively). A number of amino acid sites were found to be "diagnostic" for Hsp68 (28 of approximately 635 residues). A few of these occur in the ATPase domain (385 residues) but most (75%) are concentrated in the beta-sheet and alpha-helix domains (34% of the protein) with none in the short mobile domain. Five of the diagnostic sites in the beta-sheet domain are clustered around, but not coincident with, functional sites known to be involved in substrate binding. Nearly all of the Hsp70 family length variation occurs in the mobile domain. Within montium subgroup species, 2 nearly identical hsp68 PCR products that differed in length are either different alleles or products of an ancestral hsp68 duplication.
Kellett
Mark
M
Centre for Environmental Stress and Adaptation Research, School of Biological Sciences, Monash University, Victoria, Australia.
McKechnie
Stephen W
SW
D000251:Adenosine Triphosphatases / Q000737:chemistry / Q000235:genetics; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D017124:Conserved Sequence; D004330:Drosophila / Q000235:genetics*; D029721:Drosophila Proteins / Q000737:chemistry / Q000145:classification* / Q000235:genetics*; D004331:Drosophila melanogaster / Q000235:genetics; D014644:Genetic Variation; D018840:HSP70 Heat-Shock Proteins / Q000737:chemistry / Q000145:classification* / Q000235:genetics*; D008969:Molecular Sequence Data; D010802:Phylogeny; D017433:Protein Structure, Secondary / Q000235:genetics; D017434:Protein Structure, Tertiary / Q000235:genetics; D013379:Substrate Specificity / Q000235:genetics
D029721:Drosophila Proteins; D018840:HSP70 Heat-Shock Proteins; C490785:Hsp68 protein, Drosophila; D000251:Adenosine Triphosphatases