Article Abstract:
The binding domain for phorbol 13-acetate on the cys2 domain of protein kinase C-delta (PKC-delta) is formed by pulling apart the two beta-sheets and five hydrogen bonds are formed between the phorbol and PKC-delta. The binding of phorbol to the protein forms a hydrophobic surface which extends over 1/3 of the domain and the formation of the hydrogen bonds and the free energy released helps in the insertion of the protein into the membrane. The insertion of the unliganded protein into the membrane is unfavorable because hydrogen bonds at the membrane-protein interface are not formed.
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Article Abstract:
The structure of type II-beta phosphatidylinositol phosphate kinase (PIPK) shows a protein kinase ATP-binding core. It indicates that all phosphoinositide kinases are part of one superfamily. The flatness of the membrane-binding site, along with the shallowness of the substrate-binding pocket and its closeness to the membrane indicate that PIPKs phosphyorylate their substrates in situ in membranes. This allows the enzyme to avoid an energetic penalty for removing the substrate from its low-energy conformation within the membrane.
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Article Abstract:
The crystal structure at 3.2 angstron unit resolution of one such protein, beta 2-chimaerin, a GTPase-activating protein for the small GTPase Rac, in its inactive conformation is reported. The structure shows that in the inactive state, the N terminus of beta2-chimaerin protrudes into the inactive site of the RacGAP domain, sterically blocking Rac binding.
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