Probing the Role of the C−H···O Hydrogen Bond Stabilized Polypeptide Chain Reversal at the C-terminus of Designed Peptide Helices. Structural Characterization of Three Decapeptides

2003 ◽  
Vol 125 (49) ◽  
pp. 15065-15075 ◽  
Author(s):  
Subrayashastry Aravinda ◽  
Narayanaswamy Shamala ◽  
Abhishek Bandyopadhyay ◽  
Padmanabhan Balaram
Keyword(s):  
Hydrogen Bond ◽  
Structural Characterization ◽  
Polypeptide Chain ◽  
C Terminus ◽  
Chain Reversal

Pharmacological and structural characterization of long-sarafotoxins, a new family of endothelin-like peptides: Role of the C-terminus extension

Biochimie ◽  
2012 ◽  
Vol 94 (2) ◽  
pp. 461-470 ◽  
Author(s):  
Gilles Mourier ◽  
Mariana Hajj ◽  
Florence Cordier ◽  
Adelajda Zorba ◽  
XingHuang Gao ◽  
...  
Keyword(s):  
Structural Characterization ◽  
New Family ◽  
C Terminus

scholarly journals Characterization of hybrid proteins consisting of the catalytic domains of Clostridium and Ruminococcus endoglucanases, fused to Pseudomonas non-catalytic cellulose-binding domains

1991 ◽  
Vol 279 (3) ◽  
pp. 787-792 ◽  
Author(s):  
D M Poole ◽  
A J Durrant ◽  
G P Hazlewood ◽  
H J Gilbert
Keyword(s):  
Catalytic Domain ◽  
Binding Capacity ◽  
Binding Domains ◽  
Hybrid Proteins ◽  
C Terminus ◽  
N Terminus ◽  
Fusion Enzymes ◽  
Cellulose Binding

The N-terminal 160 or 267 residues of xylanase A from Pseudomonas fluorescens subsp. cellulosa, containing a non-catalytic cellulose-binding domain (CBD), were fused to the N-terminus of the catalytic domain of endoglucanase E (EGE') from Clostridium thermocellum. A further hybrid enzyme was constructed consisting of the 347 N-terminal residues of xylanase C (XYLC) from P. fluorescens subsp. cellulosa, which also constitutes a CBD, fused to the N-terminus of endoglucanase A (EGA) from Ruminococcus albus. The three hybrid enzymes bound to insoluble cellulose, and could be eluted such that cellulose-binding capacity and catalytic activity were retained. The catalytic properties of the fusion enzymes were similar to EGE' and EGA respectively. Residues 37-347 and 34-347 of XYLC were fused to the C-terminus of EGE' and the 10 amino acids encoded by the multiple cloning sequence of pMTL22p respectively. The two hybrid proteins did not bind cellulose, although residues 39-139 of XYLC were shown previously to constitute a functional CBD. The putative role of the P. fluorescens subsp. cellulosa CBD in cellulase action is discussed.

Hybrid αγ Polypeptides: Structural Characterization of a C12/C10Helix with Alternating Hydrogen-Bond Polarity

2008 ◽  
Vol 47 (34) ◽  
pp. 6430-6432 ◽  
Author(s):  
Prema G. Vasudev ◽  
Sunanda Chatterjee ◽  
Kuppanna Ananda ◽  
Narayanaswamy Shamala ◽  
Padmanabhan Balaram
Keyword(s):  
Hydrogen Bond ◽  
Structural Characterization ◽  
Bond Polarity

Role of Cytochrome B559 in Photoinhibition

1995 ◽  
Author(s):  
Itzhak Ohad ◽  
Himadri Pakrasi
Keyword(s):  
Water Oxidation ◽  
Electron Flow ◽  
D1 Protein ◽  
Cytochrome B559 ◽  
Low Light ◽  
C Terminus ◽  
Genes Encoding ◽  
Processing Protease

The aim of this research project was to obtain information on the role of the cytochrome b559 in the function of Photosystem-II (PSII) with special emphasis on the light induced photo inactivation of PSII and turnover of the photochemical reaction center II protein subunit RCII-D1. The major goals of this project were: 1) Isolation and sequencing of the Chlamydomonas chloroplast psbE and psbF genes encoding the cytochrome b559 a and b subunits respectively; 2) Generation of site directed mutants and testing the effect of such mutation on the function of PSII under various light conditions; 3) To obtain further information on the mechanism of the light induced degradation and replacement of the PSII core proteins. This information shall serve as a basis for the understanding of the role of the cytochrome b559 in the process of photoinhibition and recovery of photosynthetic activity as well as during low light induced turnover of the D1 protein. Unlike in other organisms in which the psbE and psbF genes encoding the a and b subunits of cytochrome b559, are part of an operon which also includes the psbL and psbJ genes, in Chlamydomonas these genes are transcribed from different regions of the chloroplast chromosome. The charge distribution of the derived amino-acid sequences of psbE and psbF gene products differs from that of the corresponding genes in other organisms as far as the rule of "positive charge in" is concerned relative to the process of the polypeptide insertion in the thylakoid membrane. However, the sum of the charges of both subunits corresponds to the above rule possibly indicating co-insertion of both subunits in the process of cytochrome b559 assembly. A plasmid designed for the introduction of site-specific mutations into the psbF gene of C. reinhardtii. was constructed. The vector consists of a DNA fragment from the chromosome of C. reinhardtii which spans the region of the psbF gene, upstream of which the spectinomycin-resistance-conferring aadA cassette was inserted. This vector was successfully used to transform wild type C. reinhardtii cells. The spectinomycin resistant strain thus obtained can grow autotrophically and does not show significant changes as compared to the wild-type strain in PSII activity. The following mutations have been introduced in the psbF gene: H23M; H23Y; W19L and W19. The replacement of H23 involved in the heme binding to M and Y was meant to permit heme binding but eventually alter some or all of the electron transport properties of the mutated cytochrome. Tryptophane W19, a strictly conserved residue, is proximal to the heme and may interact with the tetrapyrole ring. Therefore its replacement may effect the heme properties. A change to tyrosine may have a lesser affect on the potential or electron transfer rate while a replacement of W19 by leucine is meant to introduce a more prominent disturbance in these parameters. Two of the mutants, FW19L and FH23M have segregated already and are homoplasmic. The rest are still grown under selection conditions until complete segregation will be obtained. All mutants contain assembled and functional PSII exhibiting an increased sensitivity of PSII to the light. Work is still in progress for the detailed characterization of the mutants PSII properties. A tobacco mutant, S6, obtained by Maliga and coworkers harboring the F26S mutation in the b subunit was made available to us and was characterized. Measurements of PSII charge separation and recombination, polypeptide content and electron flow indicates that this mutation indeed results in light sensitivity. Presently further work is in progress in the detailed characterization of the properties of all the above mutants. Information was obtained demonstrating that photoinactivation of PSII in vivo initiates a series of progressive changes in the properties of RCII which result in an irreversible modification of the RCII-D1 protein leading to its degradation and replacement. The cleavage process of the modified RCII-D1 protein is regulated by the occupancy of the QB site of RCII by plastoquinone. Newly synthesized D1 protein is not accumulated in a stable form unless integrated in reassembled RCII. Thus the degradation of the irreversibly modified RCII-D1 protein is essential for the recovery process. The light induced degradation of the RCII-D1 protein is rapid in mutants lacking the pD1 processing protease such as in the LF-1 mutant of the unicellular alga Scenedesmus obliquus. In this case the Mn binding site of PSII is abolished, the water oxidation process is inhibited and harmful cation radicals are formed following light induced electron flow in PSII. In such mutants photo-inactivation of PSII is rapid, it is not protected by ligands binding at the QB site and the degradation of the inactivated RCII-D1 occurs rapidly also in the dark. Furthermore the degraded D1 protein can be replaced in the dark in absence of light driven redox controlled reactions. The replacement of the RCII-D1 protein involves the de novo synthesis of the precursor protein, pD1, and its processing at the C-terminus end by an unknown processing protease. In the frame of this work, a gene previously isolated and sequenced by Dr. Pakrasi's group has been identified as encoding the RCII-pD1 C-terminus processing protease in the cyanobacterium Synechocystis sp. PCC 6803. The deduced sequence of the ctpA protein shows significant similarity to the bovine, human and insect interphotoreceptor retinoid-binding proteins. Results obtained using C. reinhardtii cells exposes to low light or series of single turnover light flashes have been also obtained indicating that the process of RCII-D1 protein turnover under non-photoinactivating conditions (low light) may be related to charge recombination in RCII due to back electron flow from the semiquinone QB- to the oxidised S2,3 states of the Mn cluster involved in the water oxidation process.

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