Figure 7

Rate of occurrences and expected number of simple TM helices with increasing number of TM helices in membrane proteins. Figure 7A shows the general trend that the rate of occurrences (in terms of ratio of simple TM helices) decreases exponentially as the number of TM helices increases in the protein. The ratios stabilize beyond 6 TM helices. Note that the trend is independent of the z-score thresholds of f = 1.282 (false-negative rate of 10%; see red lines) and f = 1.645 (false-negative rate of 5%; see blue lines). On the other hand, Figure 7B shows that the expected total numbers of simple helices do not plateau with increasing TM helices. Generally, the number of expected simple helices sh is about proportional to the number of TM helices nTM in the protein. The relationship between these two values is sh = 0.218nTM (goodness of fit is R² = 0.93) for f = 1.282 and sh = 0.112nTM (goodness of fit is R² = 0.82) for f = 1.645.