Arginine remarkably prolongs the lifetime of the M-intermediate in the bacteriorhodopsin photocycle at room temperature

AbstractThe lifetime of the M-intermediate in the bacteriorhodopsin photocycle was remarkably prolonged on drying a suspension of purple membrane, in arginine solution at alkaline pH. The M-intermediate could be completely accumulated under illumination (530 nm) at room temperature. The crystalline structure of purple membranes was retained after this treatment. The lifetime of the M-intermediate was found to be longer than 100 s and depended on the pH of the purple membrane suspension before drying. It was suggested that an interaction between the guanidium group of arginine and an amino acid residue played an important role in the prolongation

Two types of arrestins expressed in medaka rod photoreceptors

AbstractSimilar to visual arrestins of other vertebrates, two subtypes of medaka visual arrestins, KfhArr-R1 and KfhArr-C, are selectively expressed in rods and cones, respectively [Hisatomi et al. (1997) FEBS Lett. 411, 12–18]. We isolated a cDNA encoding the third arrestin, KfhArr-R2, from a medaka retinal cDNA library. Phylogenetic analysis of arrestin sequences suggests that KfhArr-R2 is classified into the rod arrestin subtype. In situ hybridization indicated that KfhArr-R2 mRNA is localized in most of the rod photoreceptors, suggesting that both KfhArr-R1 and -R2 are co-expressed in rods. Antisera against KfhArr-R2 recognized outer segments, but anti-KfhArr-R1 antisera reacted with cell bodies and synaptic termini in light-adapted rods. It seems likely that KfhArr-R1 and -R2 play different roles in rod photoreceptors

Hematological- and Neurological-Expressed Sequence 1 Gene Products in Progenitor Cells during Newt Retinal Development

Urodele amphibians such as Japanese common newts have a remarkable ability to regenerate their injured neural retina, even as adults. We found that hematological- and neurological-expressed sequence 1 (Hn1) gene was induced in depigmented retinal pigment epithelial (RPE) cells, and its expression was maintained at later stages of newt retinal regeneration. In this study, we investigated the distribution of the HN1 protein, the product of the Hn1 gene, in the developing retinas. Our immunohistochemical analyses suggested that the HN1 protein was highly expressed in an immature retina, and the subcellular localization changed during this retinogenesis as observed in newt retinal regeneration. We also found that the expression of Hn1 gene was not induced in mouse after retinal removal. Our results showed that Hn1 gene can be useful for detection of undifferentiated and dedifferentiated cells during both newt retinal development and regeneration

Two Guanylate Cyclase Activating Proteins in Medaka Retina

Guanylate cyclase activating protein (GCAP1 and 2) is a Ca2+-sensitive regulator of the retinal membrane guanylate cyclases (GCs). In mammalian retina, GCAP1 is localized in cones and GCAP2 is present in rods, cones and other retinal cells. Here we isolated two kinds of cDNAs encoding putative medaka GCAPs (OlGCAP1 and OlGCAP2). Sequence analysis and characterization of recombinant proteins indicate that OlGCAP1 and 2 are closely related to mammalian GCAP1 and 2, respectively, and that OlGCAP1 and 2 appear to regulate GCs in a manner similar to that of mammalian GCAPs. However, in situ hybridization and immunocytochemistry suggest that both OlGCAP1 and 2 coexist mainly in rods, and that OlGCAP1, but not OlGCAP2, is present in the inner nuclear layer and ganglion cell layer, indicating that localization of these medaka GCAPs is totally different from that of mammalian GCAPs. The Ca2+-feedback system in vertebrate retinal phototransduction may be evolved in the expression of GCs and GCAPs in photoreceptors

Photoreactions of retinochrome at very low temperatures

AbstractRetinochrome is one of the retinal proteins found in the retina of cephalopods. It catalyses the light isomerization of retinal from the all-trans to the 11-cis form. On cooling to 25 K, the absorption peak of retinochrome (λmax 490 nm) was broadened with a shoulder, showing the spectrum steepened on the long wavelength side. On irradiation with yellow-green light (550 nm), retinochrome produced an intermediate with λmax at a shorter wavelength, around 465 nm, and a lower extinction coefficient than lumiretinochrome. It changed to lunuretinochrome (λmax 475 nm) in the dark on warming to liquid nitrogen temperature. We shall call this new intermediate prelunuretinochrome

Distribution of blue-sensitive photoreceptors in amphibian retinas

AbstractPreviously, we reported that an opsin (Rc-MS) belonging to the SWS2 group opsins is expressed in bullfrog green rods [Hisatomi, O. et al., FEBS Lett., 1999, 447, 44–48]. An anti-Rc-MS antiserum recognized the cones of the Japanese common newt, Cynops pyrrhogaster, which has no green rods. We isolated a cDNA encoding an SWS2 group opsin (Cp-SWS2) from this newt and found that Cp-SWS2 is expressed in a small population of the cones. Our results suggest that SWS2 opsins can be expressed in either green rods or cones of caudata. It seems reasonable to suppose that green rods arose before amphibia were divided into caudata and anura

EXPRESSION OF BACTERIOOPSIN GENES IN ESCHERICHIA COLI

An inducible expression vector pUBO was constructed with native codons in order to express the gene of Bacteriorhodopsin (BOP) in Escherichia coli (E. coli). Vector pUBO contains lac-promoter followed by the partial structural gene of lacZ and the structural gene of BOP. The expression of this fusion protein was detected by ELISA with anti-BOP antiserum. The fusion protein obtained from E. coli trnsformed with pUBO formed approximately 0.1% of the total protein of the E. coli membrane fraction

Trimeric mutant bacteriorhodopsin, D85N, shows a monophasic CD spectrum

AbstractThe structure of mutant bacteriorhodopsin (bR), D85N, was examined by CD and X-ray diffraction at pH 7. The absorption maximum of D85N at pH 7 is located at 605 nm, which is similar to the acid-blue form of wild-type bR. D85N shows a monophasic CD band, the maximum of which is at 575 nm, although the crystalline arrangement and the trimeric structure is maintained. The acid-blue form of wild-type bR shows a biphasic CD despite the similarity in absorption spectra

The role of proboscis of the malaria vector mosquito Anopheles stephensi in host-seeking behavior

<p>Abstract</p> <p>Background</p> <p>The proboscis is an essential head appendage in insects that processes gustatory code during food intake, particularly useful considering that blood-sucking arthropods routinely reach vessels under the host skin using this proboscis as a probe.</p> <p>Results</p> <p>Here, using an automated device able to quantify CO₂-activated thermo (35°C)-sensing behavior of the malaria vector <it>Anopheles stephensi</it>, we uncovered that the protruding proboscis of mosquitoes contributes unexpectedly to host identification from a distance. Ablation experiments indicated that not only antennae and maxillary palps, but also proboscis were required for the identification of pseudo-thermo targets. Furthermore, the function of the proboscis during this behavior can be segregated from CO₂detection required to evoke mosquito activation, suggesting that the proboscis of mosquitoes divide the proboscis into a "thermo-antenna" in addition to a "thermo-probe".</p> <p>Conclusions</p> <p>Our findings support an emerging view with a possible role of proboscis as important equipment during host-seeking, and give us an insight into how these appendages likely evolved from a common origin in order to function as antenna organs.</p

LIGHT-DEPENDENT PROTON MOVEMENT AND PHOTOINTERMEDIATES ON BACTERIORHODOPSIN PHOTOCYCLE

The relationship between photointermeidates of bacteriorhbdopsin (bR) and proton uptake was investigated by a flash photolysis technique. Attention was paid to keep the sample in a light-adapted state and under the same conditions during measurements. The decay of M-intermediate (M), the formation and decay of O-intermediates (O), the recovery of bR and release and the uptake of protons were measured with a purple membrane suspension (pH 7.0, 0.5 M NaCl) at various temperatures. The following reaction scheme for the bR photocycle was deduced from the results. 1) The decay process of M consists of three components (M_, M_ and M_s). 2) O is formed from the faster component of M (M_). 3) A part of M (M_ and M_s) decays directly to bR without passing through O. 4) The uptake of protons is coupled with the decay of the slowest M (M_s). The above reaction scheme was confirmed by the results obtained from similar experiments using an analog pigment of bR, Np-bR, M of which decays much more slowly than that in native bR system