N-terminal control of small heat shock protein oligomerization: changes in aggregate size and chaperone-like function.
The small heat shock protein superfamily is composed of proteins from throughout the phylogenetic spectrum that are induced upon environmental stress. Their structural stability under stress derives in large part from the central region of the proteins, which forms two beta sheets held together by hydrophobic interactions and appears to be present in all superfamily members. The length, sequence, and amino acid composition of the N- and C-terminals, in contrast, are quite variable. The role of the N-terminal has been hypothesized to control species-specific assembly of subunits into higher level structures. To test this, a set of constructs was designed and expressed: the N-terminal sequences preceding the start of the core regions of alphaA-crystallin and HSP 16.5 from Methanococcus jannaschii were swapped; the N-terminal of each protein was removed, and replaced with a brief N-terminal extension sequence; and two nonsense N-terminal sequences of approximately the same length and hydropathicity as the original replaced the alphaA-crystallin N-terminal. All constructs, plus the original recombinant sequences, could be overexpressed except for the 16.5 N-terminal extension, and all showed chaperone-like activity except for the hybrid with the 16.5 C-terminal. Size and properties of the replacement N-terminal place limits on aggregate size. Additional restrictions are imposed by the structure of the dimer.
Eifert
Cheryl
C
Center for Biophysics and Department of Biology, Rensselaer Polytechnic Institute, Science Center, 110 8th Street, Troy, NY 12180-3590, USA.
Burgio
Michael R
MR
Bennett
Pauline M
PM
Salerno
John C
JC
Koretz
Jane F
JF
D000818:Animals; D019843:Archaeal Proteins / Q000737:chemistry; D002417:Cattle; D019281:Dimerization; D005998:Glycine / Q000737:chemistry; D006360:Heat-Shock Proteins / Q000737:chemistry*; D017017:Methanococcus / Q000378:metabolism; D008854:Microscopy, Electron; D046529:Microscopy, Electron, Transmission; D018832:Molecular Chaperones / Q000737:chemistry*; D016133:Polymerase Chain Reaction; D011485:Protein Binding; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry; D012694:Serine / Q000737:chemistry; D012967:Sodium Dodecyl Sulfate / Q000737:chemistry; D013997:Time Factors; D038202:alpha-Crystallin A Chain / Q000737:chemistry
D019843:Archaeal Proteins; C113795:HSP16.5 protein, Methanococcus jannaschii; D006360:Heat-Shock Proteins; D018832:Molecular Chaperones; D011994:Recombinant Proteins; D038202:alpha-Crystallin A Chain; D012967:Sodium Dodecyl Sulfate; D012694:Serine; D005998:Glycine