The protein consists of between 86 and 101 amino acids depending on the subtype. Proteins are responsible for nearly every task of cellular life including cell. Biology Cell Worksheets Biology Worksheet Biology Notes Cells Worksheet The collection of proteins within a cell determines its health and function. . In molecular biology Tat is a protein that is encoded for by the tat gene in HIV-1. Tat is a regulatory protein that drastically enhances the efficiency of viral transcription. Tat stands for Trans-Activator of Transcription. Tat vastly increases the level of transcription of the HIV dsDNA.