Figure 4.
Panel A: A histogram showing the distribution of lengths of all human transmembrane domains in amino acids. The horizontal axis represents the length in amino acids, ranging from 12 to 38. The vertical axis represents the percentage of transmembrane domains, with a peak around 24 amino acids. Panel B: A histogram showing the apparent free energy of membrane insertion for all transmembrane domains. The horizontal axis represents apparent free energy in kilocalories per mole, ranging from minus 5 to 5. The vertical axis represents the percentage of transmembrane domains, with a mean of positive 0.59 and a median of positive 0.57. Panel C: A heatmap displaying amino acid frequency for all transmembrane domains, subdivided into single-pass and multipass proteins. The horizontal axis lists amino acids ordered by decreasing frequency. The top three rows show amino acid frequency percentages with a color scale from low cyan to high yellow. The bottom row shows logarithm base 2 of multipass-to-single-pass frequency ratios, with blue indicating higher frequency in single-pass transmembrane domains and red indicating higher frequency in multipass transmembrane domains. Panel D: A histogram showing the distribution of apparent free energy for single-pass transmembrane domains. The horizontal axis represents apparent free energy in kilocalories per mole, ranging from minus 5 to 5. The vertical axis represents the percentage of transmembrane domains, with a mean of minus 1.89 and a median of minus 1.82. Panel E: A histogram showing the distribution of apparent free energy for multipass transmembrane domains. The horizontal axis represents apparent free energy in kilocalories per mole, ranging from minus 5 to 5. The vertical axis represents the percentage of transmembrane domains, with a mean of positive 0.89 and a median of positive 0.84.
Biophysical properties of human TMDs. (A) Histogram of length in aa of all human TMDs. (B) Histogram of apparent free energy of membrane insertion (ΔGapp, kcal/mol) for all TMDs. (C) aa frequency heatmap for all TMDs, subdivided into SP and MP proteins, with aa ordered by decreasing frequency across all TMDs. The top three rows show aa frequency (%) with a color scale from low (cyan) to high (yellow). The bottom row shows log2(MP/SP) frequency ratios, with blue indicating a higher frequency in SP TMDs and red indicating a higher frequency in MP TMDs. (D and E) As in B but for SP (D) and MP (E) proteins. SP, single pass; MP, multipass.