Structural study of the catalytic domain of PKCzeta using infrared spectroscopy and two-dimensional infrared correlation spectroscopy

Advancements of two dimensional correlation spectroscopy in protein researches

The developments of two-dimensional correlation spectroscopy (2DCOS) applications in protein studies are discussed, especially for the past two decades. The powerful utilities of 2DCOS combined with various analytical techniques in protein studies are summarized. The emphasis is on the vibration spectroscopic techniques including IR, NIR, Raman and optical activity (ROA), as well as vibration circular dichroism (VCD) and fluorescence spectroscopy. In addition, some new developments, such as hetero-spectral 2DCOS, moving-window correlation, and model based correlation, are also reviewed for their utility in the investigation of the secondary structure, denaturation, folding and unfolding changes of protein. Finally, the new possibility and challenges of 2DCOS in protein research are highlighted as well.

Two-dimensional correlation spectroscopy in protein science, a summary for past 20years

Two-dimensional correlation spectroscopy (2DCOS) has been widely used to Infrared, Raman, Near IR, Optical Activity (ROA), Vibrational Circular Dichroism (VCD) and Fluorescence spectroscopy. In addition, several new developments, such as 2D hetero-correlation analysis, moving-window two-dimensional (MW2D) correlation, model based correlation (βν and kν correlation analyses) have also well incorporated into protein research. They have been used to investigate secondary structure, denaturation, folding and unfolding changes of protein, and have contributed greatly to the field of protein science. This review provides an overview of the applications of 2DCOS in the field of protein science for the past 20 year, especially to memory our old friend, Dr. Boguslawa Czarnik-Matusewicz, for her great contribution in this research field. The powerful utility of 2DCOS combined with various analytical techniques in protein studies is summarized. The noteworthy developments and perspective of 2DCOS in this field are highlighted finally.

Curcumin modulates PKCα activity by a membrane-dependent effect

Curcumin modulates the activity of protein kinase Cα (PKCα) when assayed in the presence of vesicles including phosphatidylcholine, phosphatidylserine and diacylglycerol. Increasing concentrations of curcumin progressively increased PKCα activity at concentrations lower than 20μM, but at higher concentrations of curcumin the activity decreased although, at concentrations of curcumin of up to 100μM the activity was always higher than the basal one (in the absence of curcumin). The maximum activity was reached at 3μM curcumin, at 20 and 30mol% of phosphatidylserine, 10μM Ca(2+) and 2mol% diacylglycerol. The same type of modulation was observed when changing the concentration of phosphatidylserine, diacylglycerol and Ca(2+). No effect of curcumin was found when the activity was assayed in the presence of Triton X-100 mixed micelles which included phosphatidylserine and diacylglycerol, indicating that the effect of curcumin was membrane-dependent. The pattern of binding of PKCα to membrane vesicles as a function of curcumin concentration closely correlated with the pattern of activating effect. It was concluded that the effect of curcumin on PKCα activity was related to its effect on the membrane, which may modulate the binding of the enzyme to the membrane.

Two-dimensional infrared correlation spectroscopy study of the interaction of oxidized and reduced cytochrome c with phospholipid model membranes

We have used two-dimensional infrared correlation spectroscopy (2D-IR) to study the interaction and conformation of cytochrome c in the presence of a binary phospholipid mixture composed of a zwitterionic perdeuterated phospholipid and a negatively-charged one. The influence of the main temperature phase transition of the phospholipid model membranes on the conformation of cytochrome c has been evaluated by monitoring both the Amide I' band of the protein and the CH(2) and CD(2) stretching bands of the phospholipids. Synchronous 2D-IR analysis has been used to determine the different secondary structure components of cytochrome c which are involved in the specific interaction with the phospholipids, revealing the existence of a specific interaction between the protein with cardiolipin-containing vesicles but not with phosphatidic acid-containing ones. Interestingly, 2D-IR is capable of showing the existence of significant changes in the protein conformation at the same time that the phospholipid transition occurs. In summary, 2D-IR revealed an important effect of the phospholipid phase transition of cardiolipin on the secondary structure of oxidized cytochrome c but not to either reduced cytochrome c or in the presence of phosphatidic acid, demonstrating the existence of specific intermolecular interactions between cardiolipin and cytochrome c.

The C2 domains of classical PKCs are specific PtdIns(4,5)P2-sensing domains with different affinities for membrane binding

C2 domains are conserved protein modules in many eukaryotic signaling proteins, including the protein kinase (PKCs). The C2 domains of classical PKCs bind to membranes in a Ca(2+)-dependent manner and thereby act as cellular Ca(2+) effectors. Recent findings suggest that the C2 domain of PKCalpha interacts specifically with phosphatidylinositols 4,5-bisphosphate (PtdIns(4,5)P(2)) through its lysine rich cluster, for which it shows higher affinity than for POPS. In this work, we compared the three C2 domains of classical PKCs. Isothermal titration calorimetry revealed that the C2 domains of PKCalpha and beta display a greater capacity to bind to PtdIns(4,5)P(2)-containing vesicles than the C2 domain of PKCgamma. Comparative studies using lipid vesicles containing both POPS and PtdIns(4,5)P(2) as ligands revealed that the domains behave as PtdIns(4,5)P(2)-binding modules rather than as POPS-binding modules, suggesting that the presence of the phosphoinositide in membranes increases the affinity of each domain. When the magnitude of PtdIns(4,5)P(2) binding was compared with that of other polyphosphate phosphatidylinositols, it was seen to be greater in both PKCbeta- and PKCgamma-C2 domains. The concentration of Ca(2+) required to bind to membranes was seen to be lower in the presence of PtdIns(4,5)P(2) for all C2 domains, especially PKCalpha. In vivo experiments using differentiated PC12 cells transfected with each C2 domain fused to ECFP and stimulated with ATP demonstrated that, at limiting intracellular concentration of Ca(2+), the three C2 domains translocate to the plasma membrane at very similar rates. However, the plasma membrane dissociation event differed in each case, PKCalpha persisting for the longest time in the plasma membrane, followed by PKCgamma and, finally, PKCbeta, which probably reflects the different levels of Ca(2+) needed by each domain and their different affinities for PtdIns(4,5)P(2).