Protein signaling network assembly

The TA results obtained for 19 are noteworthy because this work outlines a method to detect PCET intermediates by transient optical spectroscopy. The propensity of PT networks to retard charge transfer rates has practical consequences for mechanistic studies of PCET reactions. Attenuated rates translate to low yields of PCET intermediates. For this reason, it is difficult to observe PCET intermediates directly by time-resolved methods. Assembly 19 shows, however, that PCET intermediates can be spectrally uncovered when the transient difference signal between Sj and Tj excited states is minimized. This procedure, which is similar to one previously exploited in studies of D-A dyads [146] and heme protein-protein complexes [147], opens the door to a host of future experiments designed to directly monitor rates of electron transfer that are strongly coupled to proton motion. 

Assembly of the large, multiprotein cleavage/polyadenyl-ation complex around the AU-rIch poly(A) signal In a pre-mRNA is analogous In many ways to formation of the transcriptlon-prelnitlatlon complex at the AT-rIch TATA box of a template DNA molecule (see Figure 11-27). In both cases, multiprotein complexes assemble cooperatively through a network of specific protein-nucleic acid and protein-protein Interactions. 

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