Strong inhibitor of ribonucleotide reductase (RNR1) and is involved in regulating dNTP production. Homodimer; disulfide-linked. Interacts with RNR1. Levels decrease during S phase. Phosphorylated by DUN1, a downstream effector of the Mec1/Rad53 checkpoint pathway, in response to DNA damage. This promotes ubiquitination of SML1 and targets it for degradation by the 26S proteasome. Present with 18800 molecules/cell in log phase SD medium.