Catalyzes the phosphorylation of methylthioribose into methylthioribose-1-phosphate in the methionine cycle. Contributes to the maintenance of AdoMet homeostasis and is required to sustain high rates of ethylene synthesis. 5-(methylsulfanyl)-D-ribose + ATP = ADP + H(+) + S-methyl-5-thio-alpha-D-ribose 1-phosphate Optimum pH is 8.5-9.0. Amino-acid biosynthesis; L-methionine biosynthesis via salvage pathway; S-methyl-5-thio-alpha-D-ribose 1-phosphate from S-methyl-5'-thioadenosine (hydrolase route): step 2/2. Homodimer. No visible phenotype under normal growth condition (PubMed:15557090). Not able to grow with methylthioadenosine (MTA) as unique source of sulfur (PubMed:15557090). Imbalanced AdoMet homeostasis in sulfur-limiting conditions associated with a retarded growth (PubMed:17144895). Belongs to the methylthioribose kinase family.