“Shape is everything: on proteins’ functions”

Proteins are often defined as the molecules that enable life thanks to the special functions they display. But what are proteins' functions? Despite their relevance in various debates, the answer to this question is often left implicit. This paper argues that a correct characterisation of proteins' functions must consider the native structure of the protein, building on Bellazzi's definition of biochemical functions: proteins' functions are dispositions associated to specific chemical and geometrical structural properties relevant for the tertiary and quaternary structure of proteins, and they contribute to specific evolved biological processes. Section 1 introduces the problem of protein's functions. Section 2 unpacks the "structure problem" and the "function problem", where the former inquiries into the function bearer of proteins' function and the second into the relevant account of function. Section 3 presents an answer to the structure problem by arguing that the focus should be on native structure. Section 4 and Sect. 5 focus on the function problem and the account defended. Section 5 also considers two specific case studies, haemoglobin and crystallins, and a critical evaluation of the account. Section 6 concludes.