Catalyzes the phosphorylation of mevalonate (MVA) to yield mevalonate-3-phosphate. Functions in an alternative mevalonate pathway, only present in extreme acidophiles of the Thermoplasmatales order, which passes through mevalonate 3-phosphate rather than mevalonate 5-phosphate. (R)-mevalonate + ATP = (R)-3-phosphomevalonate + ADP + H(+) kcat is 5.3 sec(-1) for ATP as substrate (PubMed:25422158). kcat is 5 sec(-1) for (R)-mevalonate as substrate (PubMed:24914732). Optimum pH is 8.5. Optimum temperature is 55 degrees Celsius. Isoprenoid biosynthesis; isopentenyl diphosphate biosynthesis via mevalonate pathway. Homodimer. Belongs to the GHMP kinase family.