nˈoʊt ðæt ˈiːtʃ sˈʌbjuːnˌɪt ɪz stɹˈʌktʃɚɹəli pˈoʊlɚ ænd hɐz tʊ ɐtˈætʃ tə ðə fˈɪləmənt ɪn ɐ pɚtˈɪkjʊlɚɹ ˌoːɹiəntˈeɪʃən.
Note that each subunit is structurally polar and has to attach to the filament in a particular orientation.