Short-chain poly-(R)-3-hydroxybutyrate (cPHB), a highly flexible, amphiphilic 
molecule with salt-solvating properties, is a ubiquitous constituent of 
prokaryotic and eukaryotic cells, wherein it is mainly conjugated to proteins. 
The solvating properties and cellular distribution of cPHB suggest it may be 
associated with proteins that bind and/or transfer DNA. Here we examine 
Escherichia coli protein H-NS and calf thymus histones, H1, H2A, H2B, H3, and 
H4, for the presence of cPHB. The proteins are related in that all bind to DNA 
and are implicated in the compact organization of the chromosome. The presence 
of cPHB in E. coli H-NS was first detected in Western blots of two-dimensional 
sodium dodecyl sulfate-polyacrylamide gel electrophoresis gels of total cell 
proteins, probed with anti-cPHB IgG, and then by Western blot analysis of the 
purified protein. Western blot analysis of the calf thymus histones indicated 
that each contained cPHB. The presence of cPHB in H-NS and histones was 
confirmed by chemical assay. The in vivo size of conjugated cPHB could not be 
established due to the lack of standards and degradation of cPHB during protein 
purification and storage. The molecular characteristics of cPHB and its presence 
in histone-like and histone proteins of diverse organisms suggest it may play a 
role in DNA binding and/or DNA organization.