The distribution of subunit sizes of soluble proteins in human tissues.

1. The distribution of subunit sizes of soluble proteins in human tissues has been examined by the technique of gel filtration chromatography followed by SDS polyacrylamide gel electrophoresis. 2. Up to 101 different polypeptides were identified. These appear to represent primarily the substituent polypeptides of easily solubilized 'non-enzyme' proteins. 3. The subunit sizes ranged between 7000 and 270000 and the distribution was continuous unimodal and skewed. The mean size was estimated at 54 600+/-42 900. 4. The distribution of subunit sizes and the overall mean were found to be similar to those reported for easily solubilized human enzymes and other vertebrate proteins. These results suggest that the average structural gene coding such polypeptides consists of about 1400 base pairs.