Lycopene-Family Carotenoids Confer Thermostability on Photocomplexes from a New Thermophilic Purple Bacterium.

Abstract:

:Blastochloris tepida is a newly described thermophilic purple bacterium containing bacteriochlorophyll b. Using purified light-harvesting 1 reaction center (LH1-RC) core complexes from Blc. tepida, we compared the biochemical, spectroscopic, and thermal denaturation properties of these complexes with those of its mesophilic counterpart, Blc. viridis. Besides their growth temperature optima, a striking difference between the two species was seen in the carotenoid composition of their LH1-RC complexes. The more thermostable Blc. tepida complex contained more carotenoids with longer conjugation lengths (n > 9), such as lycopenes (n = 11), and had a total carotenoid content significantly higher than that of the Blc. viridis complex, irrespective of the light intensity used for growth. The thermostability of LH1-RCs from both Blc. tepida and Blc. viridis decreased significantly in cells grown in the presence of diphenylamine, a compound that inhibits the formation of highly conjugated carotenoids. In contrast to the thermophilic purple bacterium Thermochromatium tepidum, where Ca2+ is essential for LH1-RC thermostability, Ca2+ neither was present in nor had any effect on the thermostability of the Blc. tepida LH1-RC. These results point to a mechanism that carotenoids with elongated conjugations enhance hydrophobic interactions with proteins in the Blc. tepida LH1-RC, thereby allowing the complexes to withstand thermal denaturation. This conclusion is bolstered by a structural model of the Blc. tepida LH1-RC and is the first example of photocomplex thermostability being linked to a carotenoid-based mechanism.

journal_name

Biochemistry

journal_title

Biochemistry

authors

Seto R,Takaichi S,Kurihara T,Kishi R,Honda M,Takenaka S,Tsukatani Y,Madigan MT,Wang-Otomo ZY,Kimura Y

doi

10.1021/acs.biochem.0c00192

subject

Has Abstract

pub_date

2020-06-30 00:00:00

pages

2351-2358

issue

25

eissn

0006-2960

issn

1520-4995

journal_volume

59

pub_type

杂志文章