Apparent MW of protein on-PAGE gel > real MW?

[Baohua Huang]

Hi, everyone.

A fusion protein I expressed in E. coli has a apparent MW on SDS-PAGE gel ~5 kd
lager than it's calculated MW. This protein is 303 aa residues with a 
calculated MW of 35 kd but it runs at 40 kd position on SDS-PAGE. The protein 
has very high content of basic amino acids (32 lysines,  20 arginine and 16 
histidines). My question is : does high content of basic residues make a 
protein run slower?
I would apreciate very much any hints to my question.

Baohua Huang
Ohio state Univ.