King C, Eisenberg E, Greene L
Laboratory of Cell Biology, NHLBI, National Institutes of Health, Bethesda, Maryland 20892, USA.
J Biol Chem. 1995 Sep 22;270(38):22535-40. doi: 10.1074/jbc.270.38.22535.
DnaK, the Escherichia coli hsp70 protein, interacts with DnaJ, a protein cofactor that appears to be involved in presenting protein substrates to DnaK. The yeast DnaJ homolog, YDJ1, has also been shown to interact with yeast hsp70, although the function of this interaction is unknown. In the present study, we investigated the interaction of YDJ1 with both yeast and bovine brain hsp70. We found that, in the presence of ATP, where hsp70 is normally monomeric, YDJ1 induced almost all of the yeast and bovine brain hsp70 to form large polymers, which are readily sedimentable. These polymers were much larger than the dimers and trimers of hsp70, which normally form in the presence of ADP. YDJ1 appeared to be acting catalytically since very little YDJ1 copolymerized with the hsp70, and maximum polymerization occurred at low ratios of YDJ1 to hsp70. The polymerization required ATP and was completely reversed when ATP was replaced by ADP. These data suggest that, in the presence of ATP, YDJ1 may present one hsp70 to another just as under other conditions DnaJ is able to present protein substrates to DnaK.
大肠杆菌的热休克蛋白70（hsp70）即DnaK，与DnaJ相互作用，DnaJ是一种蛋白质辅因子，似乎参与将蛋白质底物呈递给DnaK。酵母的DnaJ同源物YDJ1也已被证明与酵母hsp70相互作用，尽管这种相互作用的功能尚不清楚。在本研究中，我们研究了YDJ1与酵母和牛脑hsp70的相互作用。我们发现，在ATP存在的情况下，hsp70通常以单体形式存在，YDJ1诱导几乎所有的酵母和牛脑hsp70形成易于沉降的大聚合物。这些聚合物比通常在ADP存在下形成的hsp70二聚体和三聚体大得多。YDJ1似乎起催化作用，因为很少有YDJ1与hsp70共聚，并且在YDJ1与hsp70的低比例下发生最大聚合。聚合反应需要ATP，当ATP被ADP取代时，聚合反应完全逆转。这些数据表明，在ATP存在的情况下，YDJ1可能将一个hsp70呈递给另一个hsp70，就像在其他条件下DnaJ能够将蛋白质底物呈递给DnaK一样。
