The protonation of Tris base by HCl can be represented as follows:

$$Tris + HCl → TrisH^+ + Cl^-$$

In this reaction, the Tris base (which is a weak base) accepts a proton (H+) from the HCl (which is a strong acid), resulting in the formation of the TrisH+ cation (which is a weak acid) and the chloride ion (Cl-).