Iron-sulfur cluster biosynthesis. Molecular chaperone DnaK promotes IscU-bound [2Fe-2S] cluster stability and inhibits cluster transfer activity.
IscU functions as a scaffold for Fe-S cluster assembly and transfer, and is known to be a substrate protein for molecular chaperones. Kinetic studies of Fe-S cluster transfer from holo IscU to apo Fd in the presence of chaperone DnaK demonstrate an inhibitory effect on the rate of Fe-S cluster transfer from IscU. Binding of DnaK reduces the rate of formation of the IscU-Fd complex (greater than 8-fold), but has little influence on the intrinsic rate of iron-sulfur cluster transfer to apo Fd. Apparently the molecular chaperone DnaK does not facilitate the process of Fe-S cluster transfer from IscU. Rather, DnaK has a modest influence on the stability of the IscU-bound Fe-S cluster that may reflect a more important role in promoting cluster assembly. In accord with prior observations the cochaperone DnaJ stimulates the ATPase activity of DnaK, but has a minimal influence on IscU cluster transfer activity, either alone or in concert with DnaK.
Wu
Shu-Pao
SP
Evans Laboratory of Chemistry, The Ohio State University, 100 West 18th Avenue, Columbus, Ohio 43210, USA.
Mansy
Sheref S
SS
Cowan
J A
JA
D000595:Amino Acid Sequence; D001059:Apoproteins / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification; D003001:Cloning, Molecular; D005288:Ferredoxins / Q000378:metabolism; D050956:HSP40 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification; D006360:Heat-Shock Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification; D006801:Humans; D007506:Iron-Sulfur Proteins / Q000037:antagonists & inhibitors* / Q000096:biosynthesis* / Q000378:metabolism; D008969:Molecular Sequence Data; D011485:Protein Binding; D011499:Protein Processing, Post-Translational; D020124:Thermotoga maritima / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
D001059:Apoproteins; D001426:Bacterial Proteins; D005288:Ferredoxins; D050956:HSP40 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D007506:Iron-Sulfur Proteins