On the abundance of zinc in the evolutionarily old protein domains

Abstract

A recent paper in PNAS (1) analyzed the evolution of metalloproteins and confirmed our earlier observation on the abundance of Zn-binding proteins among the most widespread—and evolutionarily oldest—protein folds (2). Because that observation seemed to contradict the extremely low (<10−12 M) estimates of Zn levels in the primeval anoxic ocean (3), we had suggested that the first cells developed in continental Zn-rich environments (2, 4). Specifically, we proposed that hydrothermal precipitates of zinc sulfide (ZnS), similar to those seen at modern deep sea vents, catalyzed abiogenic photosynthesis of organic compounds under the solar light (2, 4). This led to the release of …