Effect of additional mutations of the GP Ib Kozak sequence on surface expression of the GP Ib-IX complex in transfected cells. Additional mutations surrounding the GP Ib start codon were made as indicated, with each successive mutation rendering the sequence closer to the consensus sequence derived by Kozak, shown at the right. Expression of the mutants is expressed as a percentage of the expression in cells transfected with the wild-type GP Ib cDNA. *The decrease in expression from these mutants as compared with wild-type GP Ib was statistically significant.