A-kinase

Helms and McCammon 1997] Helms, V., McCammon, J.A. Kinase Conformations A computational study of the effect of ligand binding. Prot. Sci. 6 (1997) 2336-2343... 

Steinberg, R. A. A kinase-negative mutant of s49 mouse lymphoma cells is defective in posttranslational maturation of catalytic subunitof cyclic amp-dependent protein kinase. Mol. Cell Biol. 11 (1991) 705-712. 

Figure 13.24 Six subfamilies of receptor tyrosine kinases involved in cell growth and differentiation. Only one or two members of each subfamily are indicated. Note that the tyrosine kinase domain is interrupted by a "kinase insert region" in some of the subfamilies. The functional significance of the cysteine-rich and immunoglobulin-like domains is unknown.

Langeberg LK, Scott JD (2005) A-kinase-anchoring proteins. J Cell Sci 118 3217-3220... 

Beene DL, Scott JD (2007) A-kinase anchoring proteins take shape. Curr Opin Cell Biol 19 192-198... 

A kinase is an enzyme that catalyzes the transfer of the terminal phosphate of a nucleotide to suitable substrates. Protein and lipidkinases play important roles in signaling. 

As mentioned above, many transcription factors are not always active. Rather the activity of transcription factors is often achieved by induced reversible modification. Most frequently is the addition of phosphate groups (phosphorylation) to Ser, Thr, or Tyr residues. For the AP-1 component c-Jun the phosphorylation at Ser63 and Ser73 enhances activity when cells are subjected to stress, e.g. radiation. Phosphorylation is, however, dispensable for c-Jun-dqDendent tissue homeostasis in the liver, indicating that certain activities do not require the regulatory enhancement. Jun-N-teiminal kinase and a kinase called RSK or p38 catalyze the phosphorylation of AP-1. 

Insulin and other growth factors result in the phosphorylation of BP-1 at five unique sites. Phosphorylation of BP-1 results in its dissociation from 4E, and it cannot rebind until critical sites are dephosphorylated. The protein kinase responsible has not been identified, but it appears to be different from the one that phos-phorylates 4E. A kinase in the mammalian target of rapamycin (mTOR) pathway, perhaps mTOR itself, is involved. These effects on the activation of 4E explain in part how insuhn causes a marked posttranscriptional... 

Staurosporine, a kinase inhibitor, also suppressed PAL transcription and enzymatic activation, which indicates that the phosphorylation of still unknown (transcription) factors happened in response to stimulation by pectic fragments. However, another staurosporine-insensitive but salicylic acid responding pathway led to the transcription of pathogenesis related (PR) genes [26]. 

Fig. 1.16 The interaction of hymenialdisine with the backbone of a kinase. Arrows mark the location and direction of hydrogen-bonding groups, the filled circles represent the hydrophobic features.

Perhaps success is based on picking the right assay format. Kashem [68] compared an HTS for a kinase using three different formats. They observed that 57% of the compounds appeared as positives in all three assays. One can only wonder about the 43% that got away. 

As mentioned in Sect. 3, it is important to establish a detailed lead profile at the beginning of a lead identification effort. Criteria vary in different lead identification or hit-to-lead groups, but generally include some or all of the following potency, functional activity, selectivity, MW, clogP, solubility, permeability, microsomal stability and/or hepatocyte clearance, and preliminary PK including oral bioavail-ability. An example of a lead profile for a kinase inhibitor project is illustrated in Table 1 [21],... 

Figure 4.5 Example of a reaction progress curve obtained by discontinuous measurement of 33P incorportation into a peptide substrate of a kinase. Each data point represents a measurement made at a discrete time point after initiation of the reaction with y-33P-ATP.

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