Rt. Cowling et Hc. Birnboim, INCORPORATION OF [P-32] ORTHOPHOSPHATE INTO INORGANIC POLYPHOSPHATES BY HUMAN GRANULOCYTES AND OTHER HUMAN CELL-TYPES, The Journal of biological chemistry, 269(13), 1994, pp. 9480-9485
When human peripheral blood granulocytes were metabolically labeled at
37-degrees-C with [P-32] orthophosphate, inorganic polyphosphates bec
ame preferentially radiolabeled. Incorporation of radiolabel into the
polymer appeared to be ATP-independent. [P-32]Polyphosphate was identi
fied by its (i) characteristic lability to acid hydrolysis, (ii) insol
ubility in barium acetate (pH 4.5), (iii) conversion to [P-32]trimetap
hosphate, (iv) hydrolysis to [P-32]orthophosphate by an exopolyphospha
tase (Saccharomyces cerevisiae scPPX1), and (v) conversion to a ''phos
phate ladder''which co-migrated on a polyacrylamide gel with a synthet
ic phosphate ladder. Also, indirect evidence suggested that the [P-32]
polyphosphate was strongly, noncovalently associated with another unkn
own molecule. Particulate fractions (13,000 x g) from lysates of human
granulocytes, skin fibroblasts, HL-60 and SK-N-SH cells, all demonstr
ated radiolabeling of polyphosphate when incubated at 37-degrees-C wit
h [P-32] orthophosphate.