Analysis of conformational motions and related key residue interactions responsible for a specific function of proteins with elastic network model

Protein collective motions play a critical role in many biochemical processes. How to predict the functional motions and the related key residue interactions in proteins is important for our understanding in the mechanism of the biochemical processes. Normal mode analysis (NMA) of the elastic network model (ENM) is one of the effective approaches to investigate the structure-encoded motions in proteins. However, the motion modes revealed by the conventional NMA approach do not necessarily correspond to a specific function of protein. In the present work, a new analysis method was proposed to identify the motion modes responsible for a specific function of proteins and then predict the key residue interactions involved in the functional motions by using a perturbation approach. In our method, an internal coordinate that accounts for the specific function was introduced, and the Cartesian coordinate space was transformed into the internal/Cartesian space by using linear approximation, where the introduced internal coordinate serves as one of the axes of the coordinate space. NMA of ENM in this internal/Cartesian space was performed and the function-relevant motion modes were identified according to their contributions to the specific function of proteins. Then the key residue interactions important for the functional motions of the protein were predicted as the interactions whose perturbation largely influences the fluctuation along the internal coordinate. Using our proposed methods, the maltose transporter (MalFGK₂) from E. Coli was studied. The functional motions and the key residue interactions that are related to the channel-gating function of this protein were successfully identified.     

Comparison of Different Buffers for Protein Extraction from Formalin-Fixed and Paraffin-Embedded Tissue Specimens

We determined the best extraction buffer for proteomic investigation using formalin-fixation and paraffin-embedded (FFPE) specimens. A Zwittergent 3–16 based buffer, sodium dodecyl sulfate (SDS)-containing buffer with/without polyethylene glycol 20000 (PEG20000), urea-containing buffer, and FFPE-FASP protein preparation kit were compared for protein extraction from different types of rat FFPE tissues, including the heart, brain, liver, lung, and kidney. All of the samples were divided into two groups of laser microdissected (LMD) and non-LMD specimens. For both kinds of specimens, Zwittergent was the most efficient buffer for identifying peptides and proteins, was broadly applicable to different tissues without impairing the enzymatic digestion, and was well compatible with mass spectrometry analysis. As a high molecular weight carrier substance, PEG20000 improved the identification of peptides and proteins; however, such an advantage is limited to tissues containing submicrograms to micrograms of protein. Considering its low lytic strength, urea-containing buffer would not be the first alternative for protein recovery. In conclusion, Zwittergent 3–16 is an effective buffer for extracting proteins from FFPE specimens for downstream proteomics analysis.     

Effects of larval competition on survival and growth in Mediterranean fruit flies

1. Larval success was compared when one, two, or three egg clutches were laid in kumquat fruits (≈ 10 ml in volume) either successively on the same day or at the rate of one clutch per day. 2. Increased clutch density was associated with a significant decrease in larval survival rate and non‐significant decreases in larval growth rate and pupal mass. 3. Larval and pupal parameters showed significantly larger variance when clutches were laid on successive days than on the same day, suggesting a competitive advantage for older larvae over younger larvae. 4. The results suggest that, in small fruit, reduced fitness due to larval competition may act against possible fitness benefits due to social facilitation among adult females, hence reducing the likelihood of non‐linear population dynamics caused by processes such as the Allee effect.     

Phosphorylation and ubiquitination of dynamin-related proteins (AtDRP3A/3B) synergically regulate mitochondrial proliferation during mitosis

The balance between mitochondrial fission and fusion is disrupted during mitosis, but the mechanism governing this phenomenon in plant cells remains enigmatic. Here, we used mitochondrial matrix‐localized Kaede protein (mt‐Kaede) to analyze the dynamics of mitochondrial fission in BY‐2 suspension cells. Analysis of the photoactivatable fluorescence of mt‐Kaede suggested that the fission process is dominant during mitosis. This finding was confirmed by an electron microscopic analysis of the size distribution of mitochondria in BY‐2 suspension cells at various stages. Cellular proteins interacting with Myc‐tagged dynamin‐related protein 3A/3B (AtDRP3A and AtDRP3B) were immunoprecipitated with anti‐Myc antibody‐conjugated beads and subsequently identified by microcapillary liquid chromatography–quadrupole time‐of‐flight mass spectrometry (CapLC Q‐TOF) MS/MS. The identified proteins were broadly associated with cytoskeletal (microtubular), phosphorylation, or ubiquitination functions. Mitotic phosphorylation of AtDRP3A/AtDRP3B and mitochondrial fission at metaphase were inhibited by treatment of the cells with a CdkB/cyclin B inhibitor or a serine/threonine protein kinase inhibitor. The fate of AtDRP3A/3B during the cell cycle was followed by time‐lapse imaging of the fluorescence of Dendra2‐tagged AtDRP3A/3B after green‐to‐red photoconversion; this experiment showed that AtDRP3A/3B is partially degraded during interphase. Additionally, we found that microtubules are involved in mitochondrial fission during mitosis, and that mitochondria movement to daughter cell was limited as early as metaphase. Taken together, these findings suggest that mitotic phosphorylation of AtDRP3A/3B promotes mitochondrial fission during plant cell mitosis, and that AtDRP3A/3B is partially degraded at interphase, providing mechanistic insight into the mitochondrial morphological changes associated with cell‐cycle transitions in BY‐2 suspension cells.     

High-performance liquid chromatographic method for the detection and quantitation of haloperidol and seven of its metabolites in microsomal preparations

An isocratic high-performance liquid chromatographic (HPLC) system was developed to analyze haloperidol and its potential metabolites. These compounds included 4-(4-chlorophenyl)-4-hydroxypiperidine (CPHP), haloperidol N-oxide (HNO), reduced haloperidol (RHAL), the 1,2,3,6-tetrahydropyridine analogue and its N-oxide, and the pyridinium ion from haloperidol (HP⁺). The HPLC system comprised a Hypersil CPS5 column with a mobile phase of acetonitrile (67%) and ammonium acetate (final concentration 10 mM) which was adjusted to pH 5.4 by acetic acid. The solvent was delivered at 1 ml/min. RHAL and CPHP were determined by an ultraviolet detector at 220 nm with a detection limit of 1 nmol/ml. All other compounds were determined at 245 nm and had a detection limit of 0.3 nmol/ml. This system was used to analyze a microsomal metabolic mixture of haloperidol. It was found that all above compounds except HNO were metabolites of haloperidol. In addition, two other metabolites were also well separated in this HPLC system which are proposed to be oxygenated haloperidol and the pyridone analogue of haloperidol. The HPLC system was used to carry out quantitative metabolic studies of haloperidol. It was found that the metabolism of haloperidol exhibits large inter-species differences. The apparent enzyme kinetic parameters were also determined using mice microsomes.