Broad-specificity nucleoside monophosphate (NMP) kinase that catalyzes the reversible transfer of the terminal phosphate group between nucleoside triphosphates and monophosphates. Has also ATPase activity. Involved in the late cytoplasmic maturation steps of the 40S ribosomal particles, specifically 18S rRNA maturation. While NMP activity is not required for ribosome maturation, ATPase activity is. Associates transiently with small ribosomal subunit protein uS11. ATP hydrolysis breaks the interaction with uS11. May temporarily remove uS11 from the ribosome to enable a conformational change of the ribosomal RNA that is needed for the final maturation step of the small ribosomal subunit. Its NMP activity may have a role in nuclear energy homeostasis. AMP and dAMP are the preferred substrates, but CMP and dCMP are also good substrates. IMP is phosphorylated to a much lesser extent. All nucleoside triphosphates ATP, GTP, UTP, CTP, dATP, dCTP, dGTP, and TTP are accepted as phosphate donors. CTP is the best phosphate donor, followed by UTP, ATP, GTP and dCTP. May be involved in regulation of Cajal body (CB) formation. {|HAMAP-Rule:MF_03173}.