Table I.

Identification of HSA21 encoded proteins

A shows the list of four human-specific peptides found in both experiments. Shown is the name of the protein, accession number (Acc. no.), the experiment in which the peptide was detected, the 47-1/D3 ratio (117/114 for experiment 1 and 114/117 for experiment 2), and the peptide sequence. In B proteins possibly expressed from HSA21 are indicated. Average 47-1/D3 ratio was determined for the seven proteins for which no specific HSA21 peptides were found. Shown are the names of the protein, average 47-1/D3 ratio for human specific peptides (Average h), peptides that are identical between mouse and human (Average m/h), and mouse-specific peptides (Average m). A t test was performed to assess whether the contribution of putative HSA21-specific expression is significant (comparison of average m/h with average m). CBR1 is in bold to indicate the significantly changed Average m/h compared to the Average m.

A
Name	Acc. no.	Experiment	Ratio 47-1/D3	Peptide sequence
HMGN1	IPI00554761	1	15.726	TEESPASDEAGEK
CSTB	IPI00021828	1	2.652	SQVVAGTNYFIK
HMGN1	IPI00554761	1	2.033	QAEVANQETK
CSTB	IPI00021828	2	3.817	VHVGDEDFVHLR

B
Name	Average h	Average m/h	Average m	t test (p value)
CSTB	3.235
HMGN1	8.88		1.078
CCT8		1.009	1.069	0.067
GART		0.865	0.908	0.093
ATP5O		0.854	0.865	0.430
PFKL		0.958	0.936	0.230
CBR1		1.214	1.040	0.044
GABPA		1.002	0.963	0.361
SON		0.877	0.993	0.141