Effect of modification of histidine residues on organization of the pigment--protein complexes of chromatium minutissimum

The effect of diethyl pyrocarbonate on chromatophores and isolated pigment--protein complexes of Chromatium minutissimum was studied. It is shown that modification of histidine residues results in the destruction of the core antenna LHI (B880) and in a spectral shift from 850 to 830 nm in the peripheral antenna LHII (B800-850). In the purple sulfur bacterium Chromatium minutissimum the pigment--protein complexes B800-B850 (peripheral antenna, LHII) and B880 (core antenna, LHI) collect and transmit the absorbed light energy to the reaction centers. The composition of pigments and proteins as well as primary structure of the majority of polypeptides in both types of complexes from various photosynthetic bacteria have been determined.     

A fully functional rod visual pigment in a blind mammal. A case for adaptive functional reorganization?

In the blind subterranean mole rat Spalax ehrenbergi superspecies complete ablation of the visual image-forming capability has been accompanied by an expansion of the bilateral projection from the retina to the suprachiasmatic nucleus. We have cloned the open reading frame of a visual pigment from Spalax that shows >90% homology with mammalian rod pigments. Baculovirus expression yields a membrane protein with all functional characteristics of a rod visual pigment (lambda(max) = 497 +/- 2 nm; pK(a) of meta I/meta II equilibrium = 6.5; rapid activation of transducin in the light). We not only provide evidence that this Spalax rod pigment is fully functional in vitro but also show that all requirements for a functional pigment are present in vivo. The physiological consequences of this unexpected finding are discussed. One attractive option is that during adaptation to a subterranean lifestyle, the visual system of this mammal has undergone mosaic reorganization, and the visual pigments have adapted to a function in circadian photoreception.     

Sequence, genomic structure and tissue expression of carp (Cyprinus carpio L.) vertebrate ancient (VA) opsin

We report the isolation and characterisation of a novel opsin cDNA from the retina and pineal of the common carp (Cyprinus carpio L.). When a comparison of the amino acid sequences of salmon vertebrate ancient opsin (sVA) and the novel carp opsin are made, and the carboxyl terminus is omitted, the level of identity between these two opsins is 81% and represents the second example of the VA opsin family. We have therefore termed this C. carpio opsin as carp VA opsin (cVA opsin). We show that members of the VA opsin family may exist in two variants or isoforms based upon the length of the carboxyl terminus and propose that the mechanism of production of the short VA opsin isoform is alternative splicing of intron 4 of the VA opsin gene. The VA opsin gene consists of five exons, with intron 2 significantly shifted in a 3' direction relative to the corresponding intron in rod and cone opsins. The position (or lack) of intron 2 appears to be a diagnostic feature which separates the image forming rod and cone opsin families from the more recently discovered non-visual opsin families (pin-opsins (P), vertebrate ancient (VA), parapinopsin (PP)). Finally, we suggest that lamprey P opsin should be reassigned to the VA opsin family based upon its level of amino acid identity, genomic structure with respect to the position of intron 2 and nucleotide phylogeny.     

Spectral tuning of a circadian photopigment in a subterranean 'blind' mammal (Spalax ehrenbergi)

Through major research advances in the study of cytoskeletal organization, an integrated view of the complexity of this system has emerged. Recent findings on the microtubule-interacting protein Mip-90, which associates with microtubules and actin filaments in different cell domains, have shed light on its roles in cytoskeletal regulation. In order to study structural features of Mip-90, we sequenced several peptide fragments. A comparative sequence analysis revealed a high degree of similarity between the primary structure of this protein and the human heat shock protein of 90 kDa (hsp-90). Taken together, the present studies indicate the identity between Mip-90 and the the beta-isoform of hsp-90 (hsp-90beta). Western blot assays with an anti-hsp-90 monoclonal antibody showed cross-reactivity of hsp-90 and Mip-90 affinity purified from HeLa cells. Furthermore, the observed structural identity of Mip-90 with the hsp-90beta was sustained by immunoblot assays using monoclonal antibodies that specifically recognize the alpha- and beta-forms of hsp-90. Comparative fingerprinting analysis, along with the evidence of a remarkably similar biochemical behavior of both hsp-90 and Mip-90 in different affinity chromatographic systems, supported these observations. These studies, along with previous investigations, provide new data to elucidate the functional significance of these interesting cellular components and its relationships with other proteins linked to the cell architecture.