Unusual photodynamic characteristics of light-oxygen-voltage domain of phototropin linked to terrestrial adaptation of Klebsormidium nitens

Abstract

Abstract Phototropin (Phot), a blue light sensing LOV domain protein, mediates blue light responses and is evolutionary conserved across the green lineage. Klebsormidium nitens, a green terrestrial alga, presents a valuable opportunity in studying adaptive responses from aquatic to land habitat transitions. We determined the crystal structure of Klebsormidium nitens Phot LOV1 domain (KnLOV1) in the dark and engineered different mutations (R60K, Q122N, D33N) to modulate the lifetime of photo recovery cycle. We observed an unusual slow recovery in native KnLOV1 domain (τ = 2467 seconds) compared to different mutants (R60K: τ = 122 seconds, Q122N: τ = 101 seconds, D33N: τ = 580 seconds). Crystal structures of native KnLOV1 and mutants revealed subtle but critical changes near the protein chromophore that is responsible for modulating protein recovery rate. Our findings shed light on the unique structural characteristics of the newly studied KnLOV1 and its evolutionary importance for phototropin mediated physiology.