It depends on your aims.

Most common for abolishing catalytic function is the change to alanine.

Some people want to mimick phosphorylation of serine so they put aspartate.

Somebody want to increase or decrease the binding pocket size so they can substitute for bulky residues (W, I) or smaller residues (G, A).

Hi there,

It all depends on what you want to show and on what is this histidine role in the protein? Is it phosphorylable or is it a catalytic histidine(need of balanced imidazolium/imidazole forms).

First I would go for Alanine mutation, which should tell you the importance of the residue for activity, stability...

Then you can go for mimicking mutations:

Phe or Tyr to mimick stacking effect of the imidazole ring of histidine

Glu to possibly mimick phosphohistidine

Gln and Asn may mimick not protonable forms of Nepsilon and Ndelta of imidazole ring respectively.

Thanx @Jiri Koubek and Dominique Liger