Mono-ADP-ribosylation is the enzymatic transfer of
ADP-ribose from
NAD(+) to acceptor
proteins catalyzed by
ADP-ribosyltransferases. Using m-aminophenylboronate affinity chromatography, 2D-gel electrophoresis, in-gel digestion and MALDI-TOF analysis we have identified eight in vitro
ADP-ribosylated
proteins in Streptomyces coelicolor, which can be classified into three categories: (i) secreted
proteins; (ii) metabolic
enzymes using
NAD(+)/
NADH or
NADP(+)/
NADPH as
coenzymes; and (iii) other
proteins. The secreted
proteins could be classified into two functional categories: SCO2008 and SC05477 encode members of the family of periplasmic extracellular solute-
binding proteins, and SCO6108 and SC01968 are secreted
hydrolases.
Dehydrogenases are encoded by SC04824 and SC04771. The other targets are GlnA (
glutamine synthetase I., SC02198) and
SpaA (
starvation-sensing
protein encoded by SC07629). SCO2008
protein and GlnA had been identified as
ADP-ribosylated
proteins in previous studies. With these results we provided experimental support for a previous suggestion that ADP-ribosylation may regulate membrane transport and localization of
periplasmic proteins. Since ADP-ribosylation results in inactivation of the target
protein, ADP-ribosylation of
dehydrogenases might modulate crucial primary metabolic pathways in Streptomyces. Several of the
proteins identified here could provide a strong connection between
protein ADP-ribosylation and the regulation of morphological differentiation in S. coelicolor.