The shape of the time curve for the aminoacylation of tRNA has been investigated using five different amino acid:tRNA ligases. Four of these enzymes showed a lag in the time curve during the early phase of the first catalytic turnover of the enzyme. In each case, the lag period could be abolished by preincubating the ligase with amino acid, ATP, and Mg2+ under conditions known to give an aminoa...

Skp1-Cdc53/Cul1-F-box (SCF) complexes constitute a class of E3 ubiquitin ligases. Recently, a multiprotein complex containing pVHL, elongin C and Cul2 (VEC) was shown to structurally and functionally resemble SCF complexes. Cdc53 and the Cullins can become covalently linked to the ubiquitin-like molecule Rub1/NEDD8. Inhibition of neddylation inhibits SCF function in vitro and in yeast and plant...

The Pseudomonas syringae protein AvrPtoB is translocated into plant cells, where it inhibits immunity-associated programmed cell death (PCD). The structure of a C-terminal domain of AvrPtoB that is essential for anti-PCD activity reveals an unexpected homology to the U-box and RING-finger components of eukaryotic E3 ubiquitin ligases, and we show that AvrPtoB has ubiquitin ligase activity. Muta...

A loss of T cell tolerance underlies the development of most autoimmune diseases. The design of therapeutic strategies to reinstitute immune tolerance, however, is hampered by uncertainty regarding the molecular mechanisms involved in the inactivation of potentially autoreactive T cells. Recently, E3 ubiquitin ligases have been shown to mediate the development of a durable state of unresponsive...

Cullins assemble the largest family of ubiquitin ligases by binding with ROC1 and various substrate receptors. CUL4 function is linked with many cellular processes, but its substrate-recruiting mechanism remains elusive. We identified a protein motif, the DWD box (DDB1-binding WD40 protein), and demonstrated the binding of 15 DWD proteins with DDB1-CUL4A. We provide evidence supporting the crit...