Highly Hydrophilic Proteins in Prokaryotes and Eukaryotes Are Common during Conditions of Water Deficit

Abstract

The late embryogenesis abundant (LEA) proteins are plant proteins that are synthesized at the onset of desiccation in maturing seeds and in vegetative organs exposed to water deficit. Here, we show that most LEA proteins are comprised in a more widespread group, which we call "hydrophilins." The defining characteristics of hydrophilins are high glycine content (>6%) and a high hydrophilicity index (>1.0). By data base searching, we show that this criterion selectively differentiates most known LEA proteins as well as additional proteins from different taxons. We found that within the genomes of Escherichia coli and Saccharomyces cerevisiae, only 5 and 12 proteins, respectively, meet our criterion. Despite their deceivingly loose definition, hydrophilins usually represent <0.2% of the proteins of a genome. Additionally, we demonstrate that the criterion that defines hydrophilins seems to be an excellent predictor of responsiveness to hyperosmosis since most of the genes encoding these proteins in E. coli and S. cerevisiae are induced by osmotic stress. Evidence for the participation of one of the E. coli hydrophilins in the adaptive response to hyperosmotic conditions is presented. Apparently, hydrophilins represent analogous adaptations to a common problem in such diverse taxons as prokaryotes and eukaryotes.

Resuscitation of Pseudomonas aeruginosa from dormancy requires hibernation promoting factor (PA4463) for ribosome preservation

“…1A). In addition, and in contrast to published results for RMF in E. coli (24)(25)(26)(27), the P. aeruginosa Δrmf mutant did not show an observable survival phenotype compared with the wild-type strain when exposed to osmotic shock, heat shock, acid stress, or sensitivity to gentamicin. In contrast, a deletion of PA4463 (Δhpf) resulted in a decrease in cell recovery following starvation (P < 0.0001).…”

The Unstructured N-terminal Region of Arabidopsis Group 4 Late Embryogenesis Abundant (LEA) Proteins Is Required for Folding and for Chaperone-like Activity under Water Deficit

“…LEA proteins have been found in all the orthodox dry seeds (embryos) where they have been searched (1,2), and they also accumulate in response to water limitation in all vegetative tissues (2,3). Most LEA proteins show high hydrophilicity, high content of small amino acids, and absence or deficit of hydrophobic residues, properties that are extended to a larger set of proteins called hydrophilins, which have been found in species from the three domains of life and that also accumulate under water deficit (2,4). The composition of these proteins is also characteristic of a group of proteins known as intrinsically disordered proteins (IDPs) (5,6).…”

The K-Segment of Maize DHN1 Mediates Binding to Anionic Phospholipid Vesicles and Concomitant Structural Changes

“…Because of high hydrophilicity, high content of Gly (.20%), and the lack of a defined threedimensional structure in the pure form (Lisse et al, 1996), DHNs have been categorized as "intrinsically disordered/unstructured proteins" or "hydrophilins" (Wright and Dyson, 1999;Garay-Arroyo et al, 2000;Tompa, 2005;Kovacs et al, 2008). On the basis of compositional and biophysical properties and their link to abiotic stresses, several functions of DHNs have been proposed, including ion sequestration (Roberts et al, 1993), water retention (McCubbin et al, 1985), and stabilization of membranes or proteins (Close, 1996(Close, , 1997.…”