A putative spectrin-containing membrane skeleton in hyphal tips of Neurospora crassa.

The apical plasma membrane (PM) is important in hyphal tip growth, where it may regulate tip extensibility via its association with an appropriate membrane skeleton (MS). By cell fractionation and immunocytochemistry we show that proteins with characteristics of actin, spectrin, and integrin are associated in a MS-like manner with the PM of Neurospora crassa hyphae. The spectrin-like protein in particular is highly concentrated at the PM in the region of maximum apical expansion. This protein shares with other spectrins immunoreactivity, molecular weight, PM association, and actin binding capacity. Its distribution in hyphae suggests that it is a dominant component of the MS in true fungi and is critical to hyphal tip growth.