排序方式: 共有56条查询结果,搜索用时 6 毫秒
51.
Kataoka K Yamaguchi K Kobayashi M Mori T Bokui N Suzuki S 《The Journal of biological chemistry》2004,279(51):53374-53378
The intermolecular electron transfer from Achromobacter cycloclastes pseudoazurin (AcPAZ) to wild-type and mutant Alcaligenes xylosoxidans nitrite reductases (AxNIRs) was investigated using steady-state kinetics and electrochemical methods. The affinity and the electron transfer reaction constant (k(ET)) are considerably lower between AcPAZ and AxNIR (K(m) = 1.34 mM and k(ET) = 0.87 x 10(5) M(-1) s(-1)) than between AcPAZ and its cognate nitrite reductase (AcNIR) (K(m) = 20 microM and k(ET) = 7.3 x 10(5) M(-1) s(-1)). A negatively charged hydrophobic patch, comprising seven acidic residues around the type 1 copper site in AcNIR, is the site of protein-protein interaction with a positively charged hydrophobic patch on AcPAZ. In AxNIR, four of the negatively charged residues (Glu-112, Glu-133, Glu-195, and Asp-199) are conserved at the corresponding positions of AcNIR, whereas the other three residues are not acidic amino acids but neutral amino acids (Ala-83, Ala-191, and Gly-198). Seven mutant AxNIRs with additional negatively charged residues surrounding the hydrophobic patch of AxNIR (A83D, A191E, G198E, A83D/A191E, A93D/G198E, A191E/G198E, and A83D/A191E/G198E) were prepared to enhance the specificity of the electron transport reaction between AcPAZ and AxNIR. The k(ET) values of these mutants become progressively larger as the number of mutated residues increases. The K(m) and k(ET) values of A83D/A191E/G198E (K(m) = 88 microM and k(ET) = 4.1 x 10(5) M(-1) s(-1)) are 15-fold smaller and 4.7-fold larger than those of wild-type AxNIR, respectively. These results suggest that the introduction of negatively charged residues into the docking surface of AxNIR facilitates both the formation of electron transport complex and the electron transfer reaction. 相似文献
52.
Shinnichiro Suzuki Sadayoshi Hirose Satoshi Sawada Akitsugu Nakahara 《Inorganica chimica acta》1985,108(3):155-157
Co(II)-substituted hemocyanin (Co(II)Hc) of the octopus, Octopus vulgaris, has been prepared by dialysis of apohemocyanin against Co(II·) ion and subsequent Chelex-treatment. The blue 50%-Co(II)Hc (half-apo Co(II)Hc), in which binuclear coppers are replaced in the hemocyanin by a single Co(II), exhibits two absorption maxima at 560 (?Co=250) and 594 nm (?Co=320 M?1 cm?1) and a shoulder near 610 nm, all of which are attributed to a dd transition of high spin Co(II) (S=3/2) with a tetrahedral geometry. The magnetic circular dichroism (MCD) spectrum in this region also suggests the existence of a tetrahedral Co(II) species in the protein. The visible absorption and MCD spectra of octopus 50%-Co(II)Hc are quite similar to those of squid 50%-Co(II)Hc described in the previous paper (S. Suzuki, J. Kino, M. Kimura, W. Mori and A. Nakahara, Inorg. Chim. Acta, 66, 41 (1982)). The formation of half-apo Co(II)Hc demonstrates that the binuclear copper sites in native octopus hemocyanin may differ from each other in coordination geometry, as in other molluscan hemocyanins, squid and snail hemocyanins. The coordination environment of the active-site Co(II) substituted for Cu in the octopus hemocyanin is the same as that of the corresponding active site of the squid hemocyanin. 相似文献
53.
Iwasaki Hidekazu; Shidara Sohsuke; Sato Hiroshi; Yoshimura Tetsuhiko; Suzuki Shinnichiro; Nakahara Akitsugu 《Plant & cell physiology》1986,27(4):733-736
Cytochrome c' has been isolated from Achromobacter xylosoxidansGIFU 1055. The absorption spectra of the oxidized and the reducedforms are almost the same as those of cytochromes c' found sofar. The reduced form combines with CO and NO. The hemoproteinis a basic protein and consists of two identical subunits witha molecular weight of 14,000. It is readily autooxidizable withmidpoint redox potential of + 111 mV at pH 7.2. (Received December 2, 1985; Accepted February 20, 1986) 相似文献
54.
55.
The dissociation behavior of a copolymer of glutamic acid and alanine was investigated by means of potentiometric titration at various ionic strengths. From the curves of the apparent dissociation constants versus the degree of dissociation, the intrinsic dissociation constant of the carboxyl groups in the copolymer was estimated to be 3.92. This value is different from that of -linked polyglutamic acid and is similar to those of γ-linked polyglutamic acids such as bacterial poly-γ-D-glutamic acid. An analytical method of titration was used to determine the ratio of - and γ-glutamyl residues in the copolymer. From the results of this method and from the intrinsic dissociation constant, it was concluded that the glutamyl residues in this copolymer are mostly or entirely γ-linked. 相似文献
56.