Retinal is formed from apo-carotenoids in Nostoc sp. PCC7120: in vitro characterization of an apo-carotenoid oxygenase - Archive ouverte HAL Accéder directement au contenu
Article Dans Une Revue Biochemical Journal Année : 2006

Retinal is formed from apo-carotenoids in Nostoc sp. PCC7120: in vitro characterization of an apo-carotenoid oxygenase

Daniel Scherzinger
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Sandra Ruch
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Daniel Paul Kloer
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Annegret Wilde
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Salim Al-Babili
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Résumé

The sensory rhodopsin from Anabaena (Nostoc) sp. PCC7120 is the first cyanobacterial retinylidene protein identified. Here, we report on NosACO, encoded by the ORF all4284, as the candidate responsible for the formation of the required chromophore, retinal. In contrast to enzymes from animals, NosACO converts {beta}-apo-carotenals instead of {beta}-carotene into retinal in vitro. The identity of the enzymatic products was proven by HPLC and GC-MS. NosACO exhibits a wide substrate specificity with respect to chain lengths and functional end-groups converting {beta}-apo-carotenals, (3R)-3-OH- {beta}-apo-carotenals and the corresponding alcohols into retinal and 3(R)-3-OH-retinal, respectively. However, kinetic analyses revealed very divergent K m} and V max} values. Based on the crystal structure of SynACO, a related enzyme from Synechocystis sp. PCC6803 showing similar enzymatic activity, we designed a homology model of the native NosACO. The deduced structure explains the absence of {beta}-carotene-cleavage activity and indicates that NosACO is a monotopic membrane protein. Accordingly, NosACO could be readily reconstituted into liposomes . To localize SynACO in vivo, a Synechocystis knock-out strain was generated expressing SynACO as the sole carotenoid oxygenase. Western blot analyses showed that the main portion of SynACO occurred in a membrane-bound form.

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Dates et versions

hal-00478580 , version 1 (30-04-2010)

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Daniel Scherzinger, Sandra Ruch, Daniel Paul Kloer, Annegret Wilde, Salim Al-Babili. Retinal is formed from apo-carotenoids in Nostoc sp. PCC7120: in vitro characterization of an apo-carotenoid oxygenase. Biochemical Journal, 2006, 398 (3), pp.361-369. ⟨10.1042/BJ20060592⟩. ⟨hal-00478580⟩

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