Phosphorylates 5-amino-1-(beta-D-ribosyl)imidazole (AIRs) to form 5-amino-1-(5-phospho-beta-D-ribosyl)imidazole (AIR), an important intermediate in the purine and thiamine biosynthetic pathways (PubMed:12486071). It allows the use of exogenous aminoimidazole riboside (AIRs) to satisfy the cellular requirement for purines and thiamine (PubMed:12486071). 5-amino-1-(beta-D-ribosyl)imidazole + ATP = 5-amino-1-(5-phospho-beta-D-ribosyl)imidazole + ADP + H(+) Potassium may regulate kinase activity. Homodimer. Repressed by STM4068. Does not show significant conformational changes upon substrate binding. Disruption of the gene prevents the efficient use of AIRs as a source of thiamine. Belongs to the carbohydrate kinase PfkB family.