Divalent Cations and the Divergence of βγ-Crystallin Function.

摘要: The βγ-crystallin superfamily contains both β- and γ-crystallins of the vertebrate eye lens microbial calcium-binding proteins, all which are characterized by a common double-Greek key domain structure. βγ-crystallins long-lived structural proteins that refract light onto retina. In contrast, bind calcium ions. from tunicate Ciona intestinalis (Ci-βγ) provides potential link between these two functions. It binds with high affinity is found in light-sensitive sensory organ highly enriched metal Thus, Ci-βγ valuable for investigating evolution fold away binding toward stability apo form as part lens. Here, we investigate effect Ca2+ other divalent cations on aggregation propensity human γS-crystallin (HγS). Beyond Ca2+, capable coordinating Mg2+, Sr2+, Co2+, Mn2+, Ni2+, Zn2+, although only Sr2+ bound comparable to its preferred ion. extent tested stabilize structure correlates strongly ionic radius. none improved HγS, some them induced aggregation. Co2+ induce interacting cysteine residues, whereas Cu2+-mediated proceeds via different site.