Similarity between the bacterial histone‐like protein HU and a protein from spinach chloroplasts

The histone‐like protein HU isolated from E. coli is well conserved in prokaryotes. We show here that antiserum prepared against bacterial HU cross‐reacts with a DNA‐binding protein co‐sedimenting with the nucleoid of spinach chloroplasts. Antibodies prepared against cyanobacterial HU are more reactive than those raised against E. coli HU. The chloroplast protein resembles HU in that both appear to be composed of two related subunits.