Binding of Polyphosphates with Proteins

Many years ago, Liss and Langen (1960a,b) showed that the most highly polymerized yeast PolyP fraction, extractable only with strong alkali (0.05 M) or when kept for a long period with diluted CaCl2 solution, is apparently firmly bound to some cell components other than RNA. The removal of RNA by RNAase had no effect on the extraction rate of this PolyP fraction. It was considered that in this case PolyP was bound to a certain protein. 

numerous PolyP-binding proteins were detected in crude cell extracts from different organisms, including yeast and animals, using a filter-binding technique or affinity chromatography on PolyP-zirconia (Lorenz et al, 1994a). 

Some of the PolyP complexes with proteins are very important in cell regulatory processes. RNA polymerase isolated from the stationary-phase cells of E. coli was found to be closely bound with PolyP (Kusano and Ishihama, 1997). The ATP-dependent protease Lon formed a complex with PolyPs under degradation of ribosomal proteins at amino acids starvation (Kuroda et al, 2001). PolyP is able to compete with DNA for the DNA binding sites at histones (Schroder et al., 1999), while PolyPs can interact with non-histone proteins in the nucleus (Offenbacher and Kline, 1984). 

PolyPs and PHB have been found to be associated with ion-conducting proteins such as the human erythrocyte Ca2+-ATPase pump (Reush et al, 1997) and the Streptomyces lividans potassium channel (Reusch, 1999b). Some enzymes of PolyP metabolism, such as polyphosphate glucokinase (Phillips et al, 1999) and yeast high-molecular-weight exopolyphosphatase (Andreeva et al, 2001, 2004), can contain tightly bound PolyP. 

It is also possible that PolyPs in cells may be combined with other compounds, including polysaccharides, such as polyhexamines and chitin. PolyPs were shown to form complexes with polysaccharides of the cell wall of N. crassa, in vitro (Harold and Miller, 1961). The complex-forming reaction depended on both pH and the PolyP chain length. 

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