Novel 30 kDa protein possessing ATP-binding and chaperone activities.
A 30 kDa protein was purified from pig liver cytosol by using ATP-Sepharose and Green A column chromatography. The partial amino acid sequences of the protein (95 amino acid residues) had no similarity with any proteins recorded in data banks. The protein was able to form a stable complex with unfolded dihydrofolate reductase (DHFR). The spontaneous refolding of chemically denatured DHFR was arrested by the 30 kDa protein. This inhibition presumably results from the formation of a stable complex between the 30 kDa protein and DHFR. Bound DHFR could be released from the protein with ATP. The protein also showed protease resistance in an ATP-dependent manner. Incubation of the 30 kDa protein with 5 mM ATP resulted in its resistance to V8 protease or to trypsin treated with 1-chloro-4-phenyl-3-L-toluene-p-sulphonamidobutan-2-one. Divalent cations enhanced the ATP-protection effect. CD analysis of the 30 kDa protein showed that ATP induced an increase in the beta-pleated sheet content and a decrease in the alpha-helix content of the 30 kDa protein. These results suggest that the 30 kDa protein, a novel cytosolic protein, might have an affinity for ATP, a chaperonin activity, and and an ATP-protection effect against some proteases in vivo.
Itoh
H
H
Department of Biochemistry, Akita University School of Medicine, Akita City, Japan.
Tashima
Y
Y
D000255:Adenosine Triphosphate / Q000378:metabolism* / Q000494:pharmacology; D000595:Amino Acid Sequence; D000818:Animals; D002352:Carrier Proteins / Q000737:chemistry / Q000187:drug effects / Q000302:isolation & purification*; D002942:Circular Dichroism; D010450:Endopeptidases / Q000378:metabolism; D008099:Liver / Q000737:chemistry; D018832:Molecular Chaperones / Q000737:chemistry / Q000187:drug effects / Q000302:isolation & purification*; D008969:Molecular Sequence Data; D008970:Molecular Weight; D013552:Swine; D013762:Tetrahydrofolate Dehydrogenase / Q000378:metabolism
C108069:ATP-binding protein, liver; D002352:Carrier Proteins; D018832:Molecular Chaperones; D000255:Adenosine Triphosphate; D013762:Tetrahydrofolate Dehydrogenase; D010450:Endopeptidases