Question

protein can vary in size from approximately 40 to 34000 amino acids.

a) why. is there a lower limit to the size of proteins?

b)why is there an upper limit to the size of plypeptides?

Answer 1

a) Shorter polypeptides containing less than 40 residues cannot maintain a stable fold as there are not enough functional groups to stabilize the folded structure. Hence, around 40-50 residues of amino acids are necessary to perform a particular biochemical function. Therefore, 40-50 residues appears to be the lower limit for a functional domain size.

b) Protein sizes may range to several thousand residues in multi-functional or structural proteins. However, beyond a certain size the longer polypeptide will include increasing mistakes during transcription and translation due to the longer corresponding mRNA and gene.